In Vivo CAMERA WITH MULTIPLE SOURCES TO ILLUMINATE TISSUE AT DIFFERENT DISTANCES

ABSTRACT

An in vivo endoscope illuminates tissue using multiple sources. Light from a short-range source exits a tubular wall of the endoscope through a first illumination region that overlaps an imaging region, and the light returns through the imaging region after reflection by tissue, to form an image in a camera. Light from a long-range source exits the tubular wall through a second illumination region that does not overlap the imaging region. The endoscope of some embodiments includes a mirror, and light from an emitter for the short-range source is split and reaches the first illumination region from both sides of an optical axis of the camera. Illuminating the first illumination region with split fractions of light results in greater uniformity of illumination, than illuminating directly with an un-split beam. The energy generated by each source is changed depending on distance of the tissue to be imaged.

CROSS-REFERENCE TO PRIORITY APPLICATIONS

This application is a continuation application of and claims priorityfrom U.S. patent application Ser. No. 14/156,040 filed on Jan. 15, 2014which in turn is a continuation application of U.S. patent applicationSer. No. 12/475,435 filed on May 29, 2009, both having the title “InVivo CAMERA WITH MULTIPLE SOURCES TO ILLUMINATE TISSUE AT DIFFERENTDISTANCES”, filed by Gordon C. Wilson, which in turn claims priorityfrom U.S. Provisional Patent Application No. 61/060,068 filed on Jun. 9,2008 also having the title “In Vivo CAMERA WITH MULTIPLE SOURCES TOILLUMINATE TISSUE AT DIFFERENT DISTANCES”, also filed by Gordon C.Wilson. U.S. patent application Ser. Nos. 14/156,040 and 12/475,435 areboth incorporated by reference herein in their entireties. U.S.Provisional Patent Application No. 61/060,068 is also incorporated byreference herein in its entirety.

RE-VISIT NOTICE

Applicant hereby rescinds any disclaimer of claim scope in the parentapplication, namely U.S. application Ser. No. 14/156,040 and/or in thegrandparent application, namely U.S. application Ser. No. 12/475,435(now issued as U.S. Pat. No. 8,636,653) and/or in the correspondingprosecution history thereof and advises the US Patent and TrademarkOffice (USPTO) that the claims in the current application may be broaderthan any claim in the parent and/or in the grandparent. Applicantnotifies the USPTO of a need to re-visit the disclaimer of claim scopein the parent and grandparent applications, and to further re-visit allprior art cited in the parent and grandparent applications, includingbut not limited to cited references over which any disclaimer of claimscope was made in the parent and grandparent applications or in thecorresponding prosecution histories thereof. See Hakim v. Cannon AventGroup, PLC, 479 F.3d 1313 (Fed. Cir. 2007). Moreover, any disclaimermade in the current application should not be read into or against theparent or the grandparent.

BACKGROUND

Various prior art devices have been developed that are configured tocapture an image from within in vivo passages and cavities within anorganism's body, such as cavities, ducts, and tubular organs within thegastrointestinal (GI) tract. Several prior art devices are formed as acapsule dimensioned small enough to be swallowed. The capsule typicallyholds a camera and one or more light sources for illuminating an objectoutside the capsule whose image is recorded by the camera. Theelectronics in the capsule may be powered by batteries or by inductivepower transfer from outside the body. The capsule may also containmemory for storing captured images and/or a radio transmitter fortransmitting data to an ex vivo receiver outside the body. A commondiagnostic procedure involves a living organism (such as a human oranimal) swallowing the capsule, followed by the camera in the capsulecapturing images at various intervals as the capsule moves passivelythrough the organism's cavities formed by inside tissue walls of the GItract under the action of peristalsis.

Two general image-capture scenarios may be envisioned, depending on thesize of the organ imaged. In relatively constricted passages, such asthe esophagus and the small intestine, a capsule which is oblong and oflength less than the diameter of the passage, will naturally alignitself longitudinally within the passage. In several prior art capsules,the camera is situated under a transparent dome at one (or both) ends ofthe capsule. The camera faces down the passage so that the center of theimage is formed by a dark hole. The field of interest is the intestinalwall at the periphery of the image.

FIG. 1A illustrates an in vivo camera capsule 100 of the prior art.Capsule 100 includes a housing that can travel in vivo inside an organ102, such as an esophagus or a small intestine, within an interiorcavity 104 of the organ. In the image-capture scenario shown in FIG. 1A,capsule 100 is in contact with an inner surface 106 of the organ, andthe camera lens opening 110 captures images within its field of view128. The capsule 100 may include an output port 114 for outputting imagedata, a power supply 116 for powering components of the camera, a memory118 for storing images, compression circuitry 120 for compressing imagesto be stored in memory, an image processor 122 for processing imagedata, and LEDs 126 for illuminating surface 106 of the organ so thatimages can be captured from the light that is scattered off of thesurface.

A second scenario occurs when a capsule is in a cavity, such as thecolon, whose diameter is larger than any dimension of the capsule. Inthis scenario the capsule orientation is much less predictable, unlesssome mechanism stabilizes it. Assuming that the organ is empty of food,feces, and fluids, the primary forces acting on the capsule are gravity,surface tension, friction, and the force of the cavity wall pressingagainst the capsule. The cavity applies pressure to the capsule, both asa passive reaction to other forces such as gravity pushing the capsuleagainst it and as the periodic active pressure of peristalsis. Theseforces determine the dynamics of the capsule's movement and itsorientation during periods of stasis. The magnitude and direction ofeach of these forces is influenced by the physical characteristics ofthe capsule and the cavity. For example, the greater the mass of thecapsule, the greater the force of gravity will be, and the smoother thecapsule, the less the force of friction. Undulations in the wall of thecolon tend to tip the capsule such that a longitudinal axis 118 of thecapsule is not parallel to the longitudinal axis of the colon.

FIG. 1B shows an example of a passage 134, such as a human colon, withcapsule 100 in contact with surface 132 on the left side of the figure.In this case, an optical axis (not shown) of the camera is parallel tothe longitudinal axis of passage 134 (both axes are oriented verticallyin the figure). Capsule 100 also has a longitudinal axis 118 that iscoincident with its camera's optical axis. A ridge 136 in passage 134has a front surface 138 which is visible and thus imaged by capsule 100as it approaches the ridge (assuming capsule 100 moves upwards in thefigure). Backside 140 of ridge 136, however, is not visible to the lensopening 110, and hence does not form an image of backside 140.Specifically, capsule 100 misses part of surface 140 and note that itmisses an irregularity in passage 134, illustrated as polyp 142.

In FIG. 1B, three points within the field of view of lens opening 110are labeled A, B and C. The distance of lens opening 110 is differentfor these three points, where the range of the view 112 is broader onone side of the capsule than the other, so that a large depth of fieldis required to produce adequate focus for all three simultaneously.Also, if the LED (light emitting diode) illuminators provide uniformflux across the angular FOV, then point A will be more brightlyilluminated than points B and C. Thus, an optimal exposure for point Bresults in over exposure at point A and under exposure at point C. Anoptimal exposure for point A results in under exposure at points B andC. For each image, only a relatively small percentage of the FOV willhave proper focus and exposure, making the system inefficient. Power isexpended on every portion of the image by the flash and by the imager,which might be an array of CMOS or CCD pixels. Moreover, without imagecompression, further system resources are expended to store or transmitportions of images with low information content. In order to maximizethe likelihood that all surfaces within the colon are adequately imaged,a significant redundancy, that is, multiple overlapping images, isrequired in using this prior art capsule.

U.S. Pat. No. 6,836,377 and U.S. Pat. No. 6,918,872 disclose two priorart geometries for non-panoramic capsule cameras. In U.S. Pat. No.6,836,377, the capsule dome is ellipsoidal with the pupil at its centerand LEDs lying on the focal curve. In U.S. Pat. No. 6,918,872, the domeis spherical with the pupil centered on the center of curvature and LEDsin the same plane further toward the edge of the sphere. Thejust-described two patents are incorporated by reference herein in theirentirety, as background. Various illumination geometries for capsuleendoscopes with panoramic imaging systems are disclosed in U.S. patentapplication Ser. No. 11/642,285 filed on Dec. 19, 2006 by Kang-Huai Wangand Gordon Wilson entitled “In Vivo Sensor with Panoramic Camera” andassigned to CapsoVision, Inc. The just-described patent application isincorporated by reference herein in its entirety.

US Patent Publication 2006/0178557 by Mintchev et al. entitled“Self-Stabilizing Encapsulated Imaging System” is incorporated byreference herein in its entirety as background. This publicationdescribes a capsule endoscope illustrated in FIG. 1C attached hereto,wherein a light emitting diode (LED) 154 and an imager 152 (e.g. a CMOSimager) are mounted in a central region of a capsule, between ends 156 aand 156 b. The capsule includes an RF transmitter 158 that transmitsimages acquired by imager 152 to an external receiver. The capsule alsoincludes batteries 160 a and 160 b, and a controller 162.

The inventor believes that improvements in illumination for imaging invivo passages by endoscopes are desired.

SUMMARY

In accordance with the invention, an endoscope provides illuminationinside a body cavity using multiple sources of light, and capturesimages of tissue in the body cavity using a camera enclosed therein. Incertain embodiments of the invention, one of the sources (also called“long-range source”) is used to image tissue located in a predetermineddistance range from the endoscope. In the just-described embodiments,tissue located in contact with or close to (e.g. within 5 mm of) theendoscope is illuminated by another of the sources (also called“short-range source”).

The just-described two light sources may be positioned relative to thecamera as described next, based on (1) a point of intersection of anoptical axis of the camera with an inner surface of a housing of theendoscope, hereinafter “optical-axis intersection point” or simply“intersection point”; (2) one region (hereinafter “long-rangeillumination region”) of the housing through which light (also called“long-range light”) from the long-range source exits the housing; and(3) another region (hereinafter “short-range illumination region”) ofthe housing through which light (also called “short-range light”) fromthe short-range source exits the housing. Specifically, the short-rangelight source and the long-range light source are positioned such thatthe optical-axis intersection point is contained within (and is aportion of) the short-range illumination region, but the optical-axisintersection point is located outside the long-range illuminationregion.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B illustrate, in cross-sectional diagrams, a prior artcapsule endoscope in a small intestine and a large intestinerespectively.

FIG. 1C illustrates, in a perspective cut-away view, a prior artendoscope described in US Patent Publication 2006/0178557 by Mintchev etal.

FIG. 2A illustrates, in a perspective view, a capsule endoscope 200 inone embodiment of the invention, having a tubular wall 201M with animaging region 212 overlapping an illumination region 210 through whichlight is transmitted for short-range illumination and anotherillumination region 211 through which light is transmitted forlong-range illumination.

FIGS. 2B and 2C illustrate, in perspective views, the capsule endoscopeof FIG. 2A, when viewed from the left of FIG. 2A, showing overlappingbeams of illumination (FIG. 2B) and a coalesced region formed thereby(FIG. 2C).

FIG. 2D illustrates, in a perspective view, an arrangement of lightsources within the capsule endoscope of FIG. 2A.

FIG. 2E illustrates, a cross-sectional view of the capsule endoscope200, taken in the direction 2E-2E in FIG. 2C.

FIG. 2F illustrates, a cross-sectional view of the another capsuleendoscope in accordance with the invention.

FIG. 2G illustrates an endoscope in still another embodiment of theinvention, wherein the tubular wall has a central region of a diameterlarger than the two ends.

FIG. 2H illustrates an endoscope in another embodiment of the invention,wherein the tubular wall has an aspect ratio less than 1.

FIG. 2I illustrates, in a graph, the radiant energy generated by a lowerLED 217 and an upper LED 205 illustrated in FIG. 2E, depending ondistance of tissue from the endoscope.

FIGS. 2J and 2K illustrate distribution of intensity of light beams andspot sizes, at different distances, in response to current applied toLEDs 217 and 205 to generate radiant energy as illustrated in FIG. 2I.

FIGS. 2L and 2M illustrate the endoscope of FIG. 2A with multipleshort-range sources enclosed in the housing, positioned at a commonlatitude relative to the optical axis but located at differentlongitudes (i.e. radial directions).

FIG. 2N illustrates use of the endoscope of FIGS. 2L and 2M in normaloperation, wherein the multiple short-range sources create successivelyoverlapping regions spanning 360°.

FIG. 2O illustrates lenses L1-L4 and sensors Q1-Q4 that are alsoenclosed in an endoscope of the type illustrated in FIGS. 2L, 2M and 2N.

FIG. 2P illustrates an endoscope that includes a distal tip of the typeillustrated in FIG. 2A, mounted at an end of an insertion tube inaccordance with the invention.

FIG. 2Q illustrates, in an enlarged cross-sectional view, the distal tipof FIG. 2P.

FIGS. 3, 4 and 5 illustrate, in cross-sectional views taken in direction2E-2E of FIG. 2C, positioning of light source(s) in three embodiments ofan endoscope, at locations outside of a field of view of a camera.

FIG. 6 illustrates, in an enlarged view of an endoscope of the typeshown in FIG. 3, an angular relationship implemented in someembodiments, between a light source, an objective lens of a camera, andsurface of the tubular wall.

FIGS. 7, 8 and 9 illustrate, in an enlarged view of an endoscope of thetype shown in FIG. 3, an optical element used in some embodiments, toreduce angular dispersion of a light emitter.

FIG. 10 illustrates an embodiment wherein the optical element isimplemented by an angular concentrator which is positioned so that itsaxis “Z” passes through a location of the light emitter.

FIG. 11 illustrates, in a perspective view, an annular angularconcentrator that is used in some embodiments of an endoscope.

FIG. 12A illustrates, in a side view an annular angular concentratorshown in FIG. 11.

FIG. 12B illustrates, in a cross-sectional view in the direction A-A, inFIG. 12C, a portion of the annular angular concentrator of FIG. 12A.

FIG. 12C illustrates, in a top elevation view, one half portion of theannular angular concentrator of FIG. 11.

FIG. 12D illustrates, in a side view in the direction D-D, in FIG. 12C,the half portion of the annular angular concentrator.

FIG. 12E illustrates, in a bottom elevation view, a half portion of theannular angular concentrator of FIG. 11.

FIG. 13 illustrates, in a cross-sectional view, relative positions of alight emitter and a compound parabolic concentrator in some embodimentsof an endoscope in accordance with the invention.

FIGS. 14A and 14B illustrate, in a top view and a side viewrespectively, an assembly of multiple light emitters and an annularconcentrator in some embodiments of an endoscope

FIGS. 15 and 16 illustrate, in cross-sectional views, two alternativeembodiments of combination of a light emitter and a concentrator, inaccordance with the invention.

FIG. 17 illustrates use of an endoscope having two light emitters, forillumination and imaging over short distances, in accordance with theinvention.

FIG. 18 illustrates use of the endoscope of FIG. 17 for long rangeillumination and imaging, also in accordance with the invention.

FIG. 19 illustrates use of an endoscope having two light emitters, foraxial illumination and imaging, in an alternative embodiment of theinvention.

FIG. 20 illustrates, in a block diagram, the numbering of LEDs and thenumbering of sectors of a sensor for use in an illumination controlmethod of the type shown in FIG. 21.

FIG. 21 illustrates, in a flow chart, a method used in some embodiments,to operate light emitters for panoramic illumination and imaging.

FIG. 22 illustrates, in a graph, timing relationships between signalsbetween a controller, LEDs and sensors in an endoscope in accordancewith the invention.

FIG. 23 illustrates, in a block diagram, electronic circuitry includingcontroller, LEDs and sensors in an endoscope in accordance with theinvention.

FIG. 24 illustrates a monolithic sensor chip wherein four regions Q1-Q4are used to capture four portions of a panoramic 360° image.

FIG. 25 illustrates dimensions of an exemplary annular mirror 218 havinga convex reflecting surface in some embodiments of the invention.

FIG. 26 illustrates dimensions of an endoscope shaped as a capsule insome embodiments of the invention.

FIG. 27 illustrates, in a partial cross-sectional view, formation ofthree virtual sources by a two-layer window in some embodiments of acapsule endoscope in accordance with the invention.

FIG. 28A-28D illustrate in a front view, relative positions of along-range illumination region 211, a short-range illumination region210 and an imaging region 212 on a window of a capsule endoscope in someembodiments of the invention.

FIGS. 28E and 28G illustrate overlap of a pair of adjacent imagingregions 282A and 282B with one another, and additionally another overlapof another pair of adjacent imaging regions 282Z and 282A with oneanother, in a capsule endoscope of the type illustrated in FIGS. 28A and28C respectively.

FIGS. 28F and 28H illustrates a union 282 of adjacent imaging regions ina capsule endoscope of the type illustrated in FIGS. 28E and 28Grespectively.

FIGS. 28I and 28J illustrate, on an unrolled tubular wall of a capsuleendoscope of the type illustrated in FIGS. 28E-28F and 28G-28Hrespectively, the position of a union 282 of imaging regions relative tothe position of another union 281 of adjacent short-range illuminationregions.

FIGS. 28K and 28L illustrate overlap of imaging region 282A with acorresponding short-range illumination region 283A, in a capsuleendoscope of the type illustrated in FIGS. 28A and 28C respectively.

FIGS. 29A, 29B and 29C illustrate, in partial cross-sectional views,geometry for positioning a light source S relative to a pupil P of acamera to eliminate or minimize capture of virtual sources in an image.

FIG. 30 illustrates, in a cross-sectional plan view, relative positionsof long-range and short-range illumination sources in a capsuleendoscope in some embodiments of the invention.

FIGS. 31 and 32 illustrate, in cross-sectional side views, twoembodiments of a capsule endoscope in accordance with the invention,housing a radially-symmetric optical element in a camera.

FIG. 33 illustrates changes in energy emitted in accordance with thisinvention relative to changes in distance of two illumination regions ofan endoscope from a gastrointestinal tract.

FIG. 34 illustrates an endoscope having two cameras at two ends of acapsule in an alternative embodiment of the invention

DETAILED DESCRIPTION

In accordance with the invention, an endoscope 200 (FIG. 2A) providesillumination inside a body cavity 241 of a diameter D, using multiplelight sources 205, 206, and captures images of tissue using a cameraenclosed therein. In some embodiments, endoscope 200 has an aspect ratiogreater than one, with a longitudinal axis 222. The orientation ofendoscope 200 is determined by the dimension and orientation of bodycavity 241 that itself is typically elongated. Examples of body cavity241 are various portions of the gastrointestinal tract, such as thesmall intestine and the colon (large intestine). Note that in FIG. 2A, anumber of lines 299 are used as shading on a smoothly curved surface ofhousing 201, specifically to convey a visual sense of depth in theperspective view. Similar shading lines are also used in FIGS. 2B-2D,FIGS. 2G-K, and FIGS. 2M-2P.

Referring to FIG. 2A, source 205 of endoscope 200 is a “long-rangesource” that is used to image tissue located in cavity 241 within apredetermined distance range from the endoscope, e.g. between 10 mm and35 mm. Long-range source 205 is not used when tissue of the body cavity241 is in contact with the endoscope. Instead, in-contact tissue isimaged using illumination primarily from a short-range source 206.Tissue which is close to (e.g. within 5 mm of) the endoscope, but not incontact with the endoscope, is illuminated by both sources 205 and 206in some embodiments of the invention.

Regardless of how implemented, in many embodiments multiple lightsources 205 and 206 are positioned relative to a pupil 202 (FIG. 2A) ofa camera as described next. Pupil 202 has an optical axis 203 thatintersects with an internal surface of housing 201 of endoscope 200 at apoint 204. Note that housing 201 in FIG. 2A is illustratively shown tohave no thickness, although as will be readily apparent to the skilledartisan the housing has a finite thickness (e.g. 4 mm). Point 204 isalso referred to herein as an “optical-axis intersection point” orsimply “intersection point”. Long-range source 205 is positionedrelative to lens 202 such that optical-axis intersection point 204 islocated outside of a region (also called “long-range illuminationregion”) 211 through which light (also called “long-range light”) 209transmitted by long-range source 205 exits housing 201. Moreover,short-range source 206 is positioned relative to lens 202 such thatoptical-axis intersection point 204 is located inside of another region(also called “short-range illumination region”) 210 through which light(also called “short-range light”) 208 transmitted by short-range source206 exits housing 201. Note that short-range illumination region 210 islarger than the long-range illumination region 211, by design so as toensure adequate uniformity in illumination of tissue when the tissue isclose to or touching the endoscope.

To summarize the arrangement described in the preceding paragraph, lightsources 205 and 206 are positioned such that optical-axis intersectionpoint 204 is contained within (and is a portion of) short-rangeillumination region 210, but is located outside of long-rangeillumination region 211. In the embodiment illustrated in FIG. 2A,long-range illumination region 211 not only does not encloseintersection point 204, this region 211 also does not overlap a region(also called “imaging region”) 212 of housing 201 through which light(also called “reflected light”) reflected by tissue is transmittedthrough housing 201 and is captured by the camera. In some embodiments,the specific position and orientation of light sources 205 and 206relative to pupil 202 of the camera is determined empirically, with agoal to improve uniformity in illumination of tissue, located inmultiple ranges of distances from the endoscope.

Note that stray reflected light may enter endoscope 200 through otherregions, but it is a boundary of region 212 which demarcates the lightused in forming a diagnosable image within endoscope 200. The boundaryof region 212 excludes any light which is not sensed by a sensor withinendoscope 200. Moreover, the boundary of region 212 also excludes anylight which may be sensed but is not eventually used in a diagnosableimage, e.g. light which generates a portion of an image that is“cropped” (i.e. not used) prior to diagnosis.

Imaging region 212 is typically determined by a field of view (“FOV”)214. Field of view 214 is defined by a range of angles in a planepassing through optical-axis intersection point 204 and optical axis 203over which tissue 241 located outside housing 201 forms an imagecaptured by the camera for diagnosis. Note that the field of view issometimes called the angle of coverage or angle of view. The field ofview depends on the focal length of an objective lens adjacent to pupil202, and the physical size of the film or sensor used to record theimage. An intersection of field of view 214 with housing 201 formsimaging region 212 of endoscope 200. In endoscope 200, each of lightsources 205 and 206 are located outside the field of view 214 so as toavoid imaging light from these sources. The aforementioned FOV refers tothe longitudinal direction; an angular field of view exists for thelateral direction as well. However, the lateral FOV is not germane tothe present discussion.

Moreover, the above-described lack of overlap between long-rangeillumination region 211 and imaging region 212 eliminates anypossibility that a virtual image (also called “ghost”), due tolong-range light 209 reflected by housing 201, is present in an imagethat is captured by the camera and used for diagnosis. In certainalternative embodiments, a ghost from reflection of long-range light bythe housing, is present in an image that is formed in the camera, and asensor is operated to exclude the ghost e.g. by cropping the image.During cropping, a part of an image in a central region thereof istransmitted by endoscope 200 to a computer for use in diagnosis, and therest of the image containing the ghost is not processed. Depending onthe embodiment, cropping is performed either by a computer locatedoutside the body, in which case the entire image is transmitted, oralternatively performed within housing 201. In the just-describedalternative embodiments, cropping is performed in electronic circuitry,e.g. by a sensor and/or by a processor (see FIG. 18).

In some embodiments of the type described above, light source 206 isdeliberately positioned so that short-range illumination region 210overlaps imaging region 212. The just-described overlap is chosen toensure that short-range light 208 illuminates tissue adequately enoughto obtain a diagnosable image in the camera, even when the tissue is incontact with an external surface of housing 201.

In embodiments of the type shown in FIG. 2A, regions 210, 211 and 212are oriented transversely e.g. on a tubular wall 201M (FIG. 2B) which isa portion of housing 201. Moreover, in FIG. 2A, tubular wall 201M formsa portion of a housing 201 that is shaped as a capsule with two domes201T and 201B located on each of the two sides of wall 201M. In theembodiment shown in FIG. 2A, tubular wall 201M is capped with adome-shaped end (or simply “dome”) 201T on one side and anotherdome-shaped end 201B on the other side, to implement a capsuleendoscope. Domes 201T and 201B constitute portions of a housing thatalso includes tubular wall 201M.

In endoscope 200 (FIG. 2A) domes 201T and 201B are not used to pass anylight to a region outside of endoscope 200. Domes 201T and 201B are alsonot used to receive any light that forms an image to be diagnosed.Instead, light exits endoscope 200 and enters endoscope 200 throughtubular wall 201M, and the just-described orientation of light relativeto the endoscope is referred to herein as “radial”. Domes 201T and 201Bare used (with tubular wall 201M) to form a water-tight housing foroptical and electronic components enclosed within endoscope 200. Notethat other embodiments of an endoscope in accordance with the inventionmay have different shapes, e.g. endoscope 290 illustrated in FIGS. 2Qand 2R has a distal tip 291 at an end of insertion tube 292. Distal tip291 also illuminates a body cavity radially, through a tubular wallsimilar to endoscope 200. Note that in alternative embodiments, regions210, 211 and 212 are oriented axially e.g. on dome 201T or dome 201B asillustrated in FIG. 19.

As discussed above, a radially-illuminating endoscope (regardless ofwhether shaped as a capsule as in FIG. 2A or as a distal tip 291 at theend of an insertion tube 292 as shown in FIGS. 2Q and 2R) providesillumination through tubular wall 201M. Tubular wall 201M may have acircular cross section, such as a cylinder or a frustum of a prolate oroblate spheroid. The endoscope's tubular wall 201M can alternativelyhave a non-circular cross section, such as an elliptical cross-section.Regardless of the cross-section, a majority of light (e.g. greater than50% of the energy) exits from endoscope 200 radially, side-ways throughtubular wall 201M (FIG. 2B) of the endoscope. Moreover, tissue-reflectedlight passes back through tubular wall 220 also laterally, to formwithin endoscope 200 an image to be diagnosed (not shown in FIG. 2B).

In several embodiments, short-range light 208 exiting an endoscope isinitially generated by a light emitter (such as an LED) within thehousing, and short-range light 208 is then split by an optical element(also within the housing) into at least two fractions that respectivelyform at least two overlapping spots on the housing. For example, FIG. 2Billustrates two spots 210A and 210B formed by two fractions ofshort-range light 208 resulting from splitting. Splitting of short-rangelight 208 into two or more fractions enables a larger area of tissue tobe illuminated by overlapping spots which provide greater uniformity inenergy distribution across the illumination region, relative to a singlespot which has a single peak in its center.

In the example shown in FIG. 2B, the two spots 210A and 210B overlap oneanother on housing 201, to form at least a majority of (i.e. greaterthan 50% of area of) short-range illumination region 210 as illustratedin FIG. 2C. In FIGS. 2B and 2C, a third spot 210C is also formed, by athird fraction of short-range light 208 and included in short-rangeillumination region 210. In one illustrative embodiment, two roughlyequal fractions (approximately 25% of energy) of short-range light 208form spots 210A and 210B. In the illustrative embodiment, anotherfraction (approximately 50% of energy) of short-range light 208 forms athird spot 210C.

As will be readily apparent to the skilled artisan, the examples ofpercentages that form the various fractions of short-range light 208 aredifferent in different embodiments. Moreover, other embodiments (notshown) split short-range light 208 into only two fractions, i.e. do notform a third spot 210C. Still other embodiments (also not shown) splitshort-range light 208 into four or more fractions, i.e. form four ormore spots of short-range illumination region 210. Moreover, alsodepending on the embodiment, the spots of short-range light 208 may ormay not coalesce together, to form a single continuous region.

In endoscope 200, the long-range illumination region 211 and theshort-range illumination region 210 may or may not overlap one another,depending on the embodiment. Also depending on the embodiment, imagingregion 212 may or may not overlap the long-range illumination region211.

In many embodiments, two spots 210A and 210B are formed by two beams 208A and 208B (FIG. 2D) that are two fractions of short-range light 208(FIG. 2A). Beams 208A and 208B are transmitted towards the interiorsurface of housing 201 by two light sources 206 and 218 respectivelythat are located on opposite sides of optical axis 203. Optical axis 203is shown in FIGS. 2A and 2D as a horizontal line and for convenience,the two sides of optical axis 203 are referred to herein as “above” and“below” the axis, although it is to be understood that the two sidesorient differently depending on the orientation of axis 203 relative tothe observer (e.g. “left” and “right” if axis 203 is orientedvertically).

Referring to FIG. 2D, light source 206 is located below optical axis 203and transmits a majority of (i.e. greater than 50% of energy in) beam208A below optical axis 203. Accordingly, optical-axis intersectionpoint 204 is located in a top portion of spot 210A. In some embodiments,a light emitter is located below optical axis 203, and this lightemitter is included in light source 206 which additionally includes anoptical element that splits short-range light 208 received from thelight emitter. Light source 206 is located below optical axis 203 andlocated sufficiently close to (e.g. in contact with) housing 201 suchthat the angles of incidence of beam 208A on housing 201 aresufficiently large, within region 212, to minimize or eliminate captureby the camera of any portion of beam 208A directly reflected by housing201.

The above-described optical element in some embodiments forms beam 208Bfrom light 208 received from the light emitter in addition to theabove-described beam 208A. Beam 208B is initially transmitted by theoptical element across optical axis 203 to light source 218. As shown inFIG. 2D, light source 218 is located above optical axis 203, andincludes a reflective surface that re-transmits a majority of beam 208Breceived from the light emitter to form spot 210B on an inner surface ofthe housing. Optical-axis intersection point 204 is located in a bottomportion of spot 210B. Note that in the embodiment illustrated in FIGS.2B-2D, bottom portion of spot 210B overlaps the top portion of spot 210Aand intersection point 204 is located within the overlap. Moreover, inthe embodiment illustrated in FIG. 2B, spots 210A and 210B are alignedrelative to one another, along a direction that is aligned withlongitudinal axis 222 (e.g. within 5°). Note that here as well, lightsource 218 is located sufficiently close to housing 201 such that theangles of incidence of beam 208B are sufficiently large to minimize oreliminate capture by the camera of any portion of beam 208B directlyreflected by housing 201.

In the illustrative embodiment shown in FIG. 2D, a third beam 208C isalso formed by the optical element in splitting short-range light 208,and beam 208C is directly incident on housing 201 to form spot 210C amajority of which is located below spot 210B (with a small overlaptherebetween). Note that spot 210C is located in illumination region 210outside of imaging region 212. Accordingly, a majority of the thirdfraction which is incident on spot 210C does not reach the camera whenthe tissue is in contact with the housing. However, beam 208C providesillumination through short-range illumination region 210 that does reachthe camera when tissue is located a short distance away from the housing(e.g. 5 mm away).

FIG. 2E illustrates an exemplary implementation of one embodiment of anendoscope 200 of the type described above in reference to FIGS. 2A-2D.Specifically, as illustrated in FIG. 2E, a light emitter 217 suppliesshort-range light to an optical element 216 that splits the short-rangelight into three beams as follows. One beam 208C (FIG. 2D) is directlyincident on the housing with intensity distribution 219C (FIG. 2E).Another beam 208A (FIG. 2D) is mostly below optical axis 203 and isincident on the housing with intensity distribution 219A (FIG. 2E). Athird beam 208B (FIG. 2D) crosses optical axis 203 and is reflected by amirror 218 and then is incident on the housing with intensitydistribution 219B (FIG. 2E). An example of optical element 216 is acompound parabolic concentrator (CPC) as discussed below. Lens L is anobjective for the camera, and light received therethrough is reflectedby a mirror M to sensor 232 for sensing and storage of the image.

Note that the implementation illustrated in FIG. 2E is symmetric aboutlongitudinal axis 222, and endoscope 200 holds four copies of a lightemitter in long-range source 205, another light emitter 217 and opticalelement 216 (together forming a short range light source), opticalelement 218 (which together with light emitter 217 and optical element216 forms another short range light source), lens L and mirror M. Notealso that sensor 232 and light emitter 217 are both supported by a board249. In another embodiment, there are a pair of light emitters in eachof eight radial directions (for a total of sixteen emitters) that areused to generate a 360° panoramic image of a body cavity.

Although an endoscope 200 illustrated in FIG. 2E, has two light emittersin a given radial direction, alternative embodiments may use four lightemitters in a single radial direction, as shown in the cross-sectionalview illustrated in FIG. 2F. In FIG. 2F, endoscope 250 includes twolight emitters 221A and 224A that are used as two long-range lightsources. Moreover, endoscope 250 also has two additional light emitters222A and 223A that are used as short-range light sources. Moreover, insome embodiments, light emitters are positioned in the endoscope toilluminate along each of four radial directions (e.g. north, south, eastand west around a circular boundary of the housing, when viewed from thetop). Three sets of light sources in corresponding three radialdirections are illustrated in FIG. 2F as sources 221A, 222A, 223A and224A in the west direction, sources 221B, 222B, 223B and 224B in thenorth direction, and sources 221C, 222C, 223C and 224C in the eastdirection (with sources in the south direction being not shown in FIG.2F because it is a cross-sectional view). In certain embodiments, lightemitters are positioned in the endoscope to illuminate along each ofeight radial directions (e.g. north, north-east, east, south-east,south, south-west, west, and north-west, again, when viewed from thetop).

The embodiment shown in FIG. 2A has an aspect ratio greater than 1,whereby endoscope 200 has a larger dimension along axis 222 than anyother dimension located within a cross-section that is transverse toaxis 222. For example, endoscope 200 has a length along tubular wall201M that is larger than the outer diameter of tubular wall 210M (incase of a circular cross-section). Accordingly, tubular wall 202 has acylindrical shape, in the just-described embodiment.

In several alternative embodiments of the invention, an endoscope has atubular wall of varying cross-section along the length of the endoscope.For example, FIG. 2G illustrates an endoscope 223 wherein a tubular wall224 has an outer diameter 225 (in case of a circular cross-section) inthe middle which is larger than an outer diameter 226 at the ends, i.e.tubular wall 224 has a bulge at its center. In another example (notshown), the tubular wall of an endoscope in accordance with theinvention has narrower central portion with wide ends, i.e. an hourglassshape. Regardless of the shape of the tubular wall, illumination andimaging are performed through various overlapping and non-overlappingregions of the tubular wall, as described above in certain embodimentsof the invention.

Furthermore, in another alternative embodiment illustrated in FIG. 2H,an endoscope 227 has an aspect ratio less than 1, whereby a dimensionalong axis 222 is smaller than at least one dimension in a cross-sectiontransverse to axis 222, e.g. thickness 229 is smaller than diameter 228(in case of a circular cross-section). Even though aspect ratio lessthan 1, in this embodiment as well, overlapping and non-overlappingregions for illumination and imaging are formed on the tubular wall 229as described above.

In one illustrative embodiment, endoscope 200 (FIG. 2B) has a diameter231 of 1.1 cm and a length 232 of 2.6 cm. Note that in this illustrativeembodiment, tubular wall 201M has a transparent window of height 5.0 mm.Moreover, imaging region 212 (FIG. 2A) has a width expressed as an arclength, of 0.9 cm and a height of 0.5 cm. Furthermore, illuminationregion 210 (FIG. 2C) does not have an exact boundary. Hence, the contourshown in FIG. 2C is for a specific intensity level, such as 10% ofmaximum intensity. In the illustrative embodiment, contour 210 has aheight of 0.7 cm and a maximum arc width of 0.7 cm. Additionally, notethat tubular wall 201M (FIG. 2B) has a length of 2.0 cm. Also, each ofdomes 201T and 201B has a height of 0.3 cm (see FIG. 2C) and a diameterof 1.1 cm (which diameter is same as the diameter of tubular wall). Notethat the dimensions identified herein are merely for illustration, andother dimensions are used in other embodiments.

In some embodiments, imaging region 212 (FIG. 2A) and illuminationregions 210 and 211 are located closer to top dome 201T (also called“near end”), and farther removed from bottom dome 201B (also called “farend”). Space adjacent within the endoscope which is enclosed within oradjacent to either or both of domes 201T and 201B is used in certainembodiments to house various electronic components, such as a batteryand a wireless transmitter (not shown) of the type normally used in acapsule endoscope.

In other embodiments, illumination and imaging regions 210 and 212overlap a half-way line (e.g. an “equator”) that is located equidistantfrom each of two farthest points on two domes 201T and 201B of a capsuleendoscope. In still other embodiments (also not shown), illumination andimaging regions 210 and 212 are centered at the half-way line and inthese embodiments the half-way line passes through optical-axisintersection point 204 (FIG. 2A; half-way line not shown). In someembodiments imaging region 212 and illumination region 210 (as shown inFIG. 2A) have their respective centers offset from one another, althoughin other embodiments the two centers are coincident.

Referring to FIG. 2A, illumination region 210 is formed by lightoriginating at short-range light source 206 that is located towards thefar end 201B. Short-range source 206 is offset in a longitudinaldirection along axis 222 from optical axis 203 by a distance 233.Long-range light source 205 is also offset from optical axis 203 in thelongitudinal direction along axis 222 similar to light source 206, butthe direction is opposite. In FIG. 2A, light source 205 is locatedtowards near end 201T at an offset distance 234 from optical axis 203.Furthermore, as shown in FIG. 2B, light source 218 is implemented by amirror that is also offset in the longitudinal direction along axis 222towards near end 201T, at an offset distance 235 from optical axis 203.

Sources 206, 205 and 218 are positioned at locations and oriented atangles that are selected to ensure that any reflection of light fromthese sources by tubular wall 201M does not enter pupil 202. In oneillustrative embodiment, short-range offset distance 233 is 0.2 cm,long-range offset distance 234 is 0.4 cm, and the mirror's offsetdistance 235 is 0.4 cm. Note that offset distances can be smaller if theangular distribution of light from the source is narrowed. Accordingly,a projection onto a longitudinal plane, of mirror-reflected rays, is ina narrow range of angles relative to rays from the other two sources,and for this reason the mirror's offset distance is also smallerrelative to the other two sources' offset distances.

In some embodiments, light sources 205 and 206 are operated to generatedifferent amounts of radiant energy relative to each other depending ondistance of tissue 241 from endoscope 200. The distance of tissue isdetermined by a controller (mounted on a printed circuit board 249) inendoscope 200 based on intensity of light reflected by the tissue andsensed by a sensor 232 of the camera. Using the sensed intensity,current applied to sources 205 and 206 are automatically changed by thecontroller (see FIG. 23), using an empirically-determined relationshipbetween radiant energy and distance. In the example illustrated in FIG.2E, the intensity distribution of light from source 205 is not shown.

Source 205 may be operated to generate a minimal amount of radiantenergy (or even switched off depending on the embodiment) if the tissueto be imaged is in contact with the endoscope 200. As noted above,in-contact tissue is illuminated by light from short-range source 206.When tissue is far away from the endoscope, multiple light sources 205,206 and 218 may all be used simultaneously, concurrently orcontemporaneously (depending on the embodiment) to provide theillumination needed to generate a diagnosable image. Accordingly, thenumber of sources used for imaging is varied depending on distance, toensure that the tissue's image is formed within the camera within apredetermined intensity range.

In some embodiments, the predetermined intensity range is selected aheadof time empirically, based on adequacy of images to enable resolution ofthe detail necessary for diagnosis by a doctor. The specific manner inwhich tissue's distance and/or light emitter energy emission aredetermined for an endoscope is different in various embodiments.Accordingly, numerous methods to determine tissue's distance and/orlight emitter energy emission will be readily apparent to the skilledartisan, in view of this disclosure.

Inclusion of multiple light sources in an endoscope in accordance withthe invention enables the endoscope to image tissue located at differentdistances from the endoscope by using illumination of different amountsand/or distributions depending on the distance of the tissue. In a firstexample, when tissue is located in contact with or at a very shortdistance D1 from an external surface of the endoscope (e.g. less than a1/10^(th) the diameter D of the body cavity of interest), tissue 241 isilluminated (and imaged) by supplying LED 217 with current to generateradiant energy E2 (FIG. 2I). The resulting illumination includesintensity distributions 219A-219C (FIG. 2J and FIG. 2K) generated byrespective beams 208A-208C via imaging region 212. At this time,long-range source LED 205 is operated to generate a negligible amount ofenergy E1 which results in a distribution 215, and a majority of itsenergy is outside of field of view 214, i.e. not used in imaging. Hencesource 205 may be turned off at this stage, if appropriate.

In a second example, tissue is located at an intermediate distance D2from the endoscope (e.g. on the order of ⅕^(th) of body cavity diameter)and as illustrated in FIG. 2I both LEDs 217 and 205 in endoscope 200 aredriven to generate the same amount of radiant energy E3. The resultingillumination now includes intensity distribution 215 (FIG. 2J and FIG.2K), a portion of which now overlaps optical axis 203, although amajority of energy is above axis 203. Note that the peak of (and hencethe center of) distribution 219B also has moved (in the longitudinaldirection) to a location above the peak of distribution 215.Furthermore, a peak of distribution 219A has moved from a location aboveaxis 203 to a location below the peak 219C. Accordingly, within thecamera's field of view 214 at intermediate distance D2, long-rangesource LED 205 provides approximately the same amount of illumination asthe illumination provided by short-range source LED 217.

In a third example, tissue is located at another intermediate distanceD3 (e.g. on the order of ⅓^(rd) of body cavity diameter) and long-rangesource LED 205 is operated to generate energy E5 (FIG. 2I) that isalmost double the energy E4 of short-range source LED 217. The intensitydistribution 215 (FIG. 2J and FIG. 2K) at distance D3 constitutes amajority of illumination (e.g. provides >50% of energy). Hence,long-range source LED 205 provides a majority of illumination. Note thatat distance D3, the peaks of distributions 219A and 219B are locatedoutside of the camera's field of view 214. While the peak ofdistribution 219C is within the field of view 214, this distribution'scontribution to the total illumination is small (e.g. less than 20%).

Finally, in a fourth example, tissue is located at a large distance D4(e.g. on the order of ½ of body cavity diameter), long-range source LED205 is supplied power P6 (FIG. 2I) that is an order of magnitude greaterthan power P4 of short-range source LED 217 (whose power P4 remains sameas at distance D3). As shown in FIG. 2K, intensity distribution 215 fromlong-range source LED 205 provides the primary illumination.Contributions, from short-range source LED 217 are minimal at distanceD4 (e.g. 5% or less).

Note that in some embodiments of the type shown in FIG. 2I, theintegration time of each pixel is shifted relative to another pixel,although the pixels have a common integration time during which timeeach of the LEDs within the endoscope is turned on, e.g. sequentiallyone after another, or all on simultaneously. Note further that theamount of radiant energy emitted by an LED (and consequently captured bya pixel) depends on the duration of time for which the LED is turned onand the power output by the LED during the time it is on. A summary ofdistances and radiant energy discussed above is provided in thefollowing table, for one specific illustrative embodiment, with numbersin the following table being examples which have different values inother embodiments. In the following table, ρ is the distance from thelongitudinal axis of endoscope to a plane in which tissue is located, Ris the radius of the endoscope, Utop is proportional to the luminousenergy of the top long-range LED, and Ubottom is proportional to theluminous energy of the short-range source LED 217

ρ/R Utop Ubottom D1 1.0 0.004 0.02 D2 1.8 0.03 0.03 D3 3.2 0.1 0.05 D47.0 1.0 0.05

The intensity distributions shown in FIGS. 2J and 2K are based onannular mirror 218 having a convex reflective surface. The intensitydistributions are roughly the same for a flat mirror 218, although theexact distribution shape becomes a bit narrower. Note that the peak indistribution 215 from light transmitted by long-range LED 205 roughlyfollows a line inclined at an angle of the LED (e.g. 20 degrees relativeto optical axis 203). So, if the tilt of LED 205 changes, the horizontaldistance at which the center of distribution 215 intersects the opticalaxis 203 also changes. This distance is given by (distance of LED fromaxis)/tan(inclination angle). In the absence of significant illuminationfrom the short-range LED, this is the distance at which the long-rangeillumination's intensity distribution is symmetrical relative to thecamera. For greater distances the distribution is less symmetrical butuniformity actually improves because the distribution spreads fasterthan the field of view expands.

As noted above, FIG. 2A illustrates radial illumination by endoscope 200in one direction (namely towards the west or left in FIG. 2A) althoughendoscope 200 has similar structure in other radial directions (e.g. 3additional directions), to enable generation of a 360° panoramic imageof tissue 241 all around within a body cavity of diameter D (FIG. 2A).Specifically, as illustrated in FIG. 2L, endoscope 200 includes, inaddition to a short-range light source LED 217, three additionalshort-range light source LEDs 242, 243 and 244 that are mounted within acommon lateral plane 251 in which LED 217 is mounted. While LED 217forms illumination region 210, other sources form other illuminationregions around the tubular wall of endoscope 200. Specifically, asillustrated in FIG. 2M, source 242 forms illumination region 252 that isat a different longitude from region 210. Note that regions 252 and 210are adjacent to one another and have an overlap such that when bothsources 217 and 242 are simultaneously turned on these two regions mergeto form a continuous region 253 as shown in FIG. 2N.

Note that endoscope 240 also includes various optical and/or electroniccomponents required to form images that may be combined by a computer(not shown) to form a continuous 360° panoramic image. For example, someembodiments use as the objective a wide-angle lens that has an extremelywide field of view (e.g. 160°). One or more additional optical elements,such as a mirror, a lens and/or a prism are included in an optical pathwithin endoscope 200 from the lens, e.g. to create an appropriate imagefor capture by a sensor. Note that in some embodiments, the additionaloptical elements include a mirror followed by three lenses that areselected to ensure low aberration and distortion and to provide anappropriate field of view as will be apparent to the skilled artisan inview of this disclosure. Certain illustrative embodiments, includeadditional optical elements as described in U.S. application Ser. No.12/463,488 entitled “Folded Imager” filed by Gordon Wilson et al on May11, 2009 which is incorporated by reference herein in its entirety.

Endoscope 200 may enclose several lenses (e.g. 4 lenses) used asobjectives in each of several longitudinal planes, and light from theobjectives passes to corresponding sensors via additional opticalelements (as necessary). FIG. 20 illustrates lenses L1-L4 that are usedas objectives for reflected light that enters the endoscope. Light fromlenses L1-L4 is reflected by mirrors (not shown in FIG. 2O; see mirror Min FIG. 2E), and passes through additional lenses to sensors Q1-Q4 forimaging therein.

Although a capsule shaped endoscope has been illustrated in FIGS. 2A-2F,in an alternative embodiment illustrated in FIG. 2P, an endoscope 290includes a distal tip 291 at an end of an insertion tube 292. Tube 292is connected to a control section 293 that in turn is connected to auniversal cord 294. As shown in FIG. 2Q, distal tip 291 includes atubular wall 291M and a top dome 291T at its near end but does not haveanother dome at the bottom. Instead, the bottom of distal tip 291 isconnected to the insertion tube 292. Note that distal tip 291illuminates a body cavity radially, through tubular wall 291M.

A capsule endoscope 300 (FIG. 3) in accordance with the invention imagesin vivo objects that are close to or touching the capsule housing by useof a lens 301 as an objective of a camera 304. Lens 301 has anassociated input pupil P (FIG. 3). Note that FIG. 3 schematicallyillustrates capsule endoscope 300 with a single objective lens 301, apupil P, and image plane I on which image 305 forms. For simplicity,camera 304 is shown in FIG. 3 modeled as a pinhole with the input andoutput pupils collocated and an angular magnification of one.

In FIG. 3, lens 301 has a field of view (FOV) directed, sideways througha window 303 in a tubular wall 351 of capsule endoscope 300. The termFOV denotes a field of view of the overall imaging system in alldirections, and is defined by the range of field angles about theoptical axis 306 that produces an image 305 on a target region R of theimage plane I. The objective lens 301 may have a larger FOV thatproduces an image that overfills the target region R on the image planeI. For example, the target region R may be defined by all the activepixels on an image sensor I or by a subset of these pixels.

A projection of the FOV in a longitudinal plane of capsule endoscope 300(FIG. 3) is referred to as longitudinal FOV. An example of longitudinalFOV is the field of view 214 in FIG. 2A. Another projection of the FOVin a lateral plane (perpendicular to the longitudinal plane) is referredto as lateral FOV. If the capsule endoscope is oriented vertically asshown in FIG. 3, the longitudinal FOV is located within a vertical plane(which is the same as the plane of the paper in FIG. 3), and the lateralFOV is in a horizontal plane (perpendicular to the plane of the paper).The longitudinal FOV spans angles on either side of optical axis 306 andis delineated by lines of perspective A and B as shown in FIG. 3.Accordingly, the lateral FOV is located in a plane that passes throughan optical axis 306 of capsule endoscope 300 (FIG. 3). The lateral FOVsof multiple objective lenses, included in capsule endoscope 300 andlocated at different longitudes, overlap at their boundaries such that a360° panorama is imaged by camera 304 as described above in reference toFIG. 2O.

A short-range light source 302 is located within the capsule endoscope300 but outside of a body of camera 304. Thus, a portion of theilluminating light from source 302 passes out through tubular wall 351via an optical window 303. Reflected image-forming light returns intothe capsule endoscope 300 through the same optical window 303 and iscollected by camera 304 to form an image 305 of the exterior object (notshown in FIG. 3). Camera 304 may also capture illumination lightreflected by the exterior surface 303E and interior surface 303I of thewindow 303. These reflections appear as light spots in image 305,degrading the image's quality and its diagnostic value.

For color imaging by capsule endoscope 300, short-range light source 302is implemented as a white light source. In some embodiments, the whitelight source is formed by use of a blue or violet LED encapsulated withphosphors that emit at longer visible wavelengths when excited by theblue or violet LED. In order to minimize the size of the cavity, an LEDwith conductive substrate is used in several embodiments, so that onlyone bond wire and associated bond pad is required. Alternatively,multiple LEDs emitting at different wavelengths, such as red, green, andblue, are combined in certain embodiments. Still other embodiments ofcapsule endoscope 300 use light sources which include organic LEDs(OLEDs), electroluminescent devices, and fluorescent sources.

In some embodiments of capsule endoscope 300, antireflection (“AR”)coatings on interior surface 303I and/or exterior surface 303E are usedto reduce these reflections. Specifically, using standard processes suchas sputtering and evaporation, AR coatings are applied to surfaces thatare roughly normal to the line-of-sight flow of material from itssource. Accordingly, antireflection coating of a tubular wall ofcylindrical shape in a capsule endoscope on its exterior surface 303E isperformed in some embodiments. Conformal coatings of materials such aspolymers or the imprintation or etching of microstructures onto thetubular wall are various techniques that are used in such embodiments toachieve an AR coating.

AR coatings, which are used on some embodiments of a capsule endoscope300, are designed to resist scratching at least as well as the polymermaterial used to form endoscope 300's tubular wall, and satisfy itsother requirements such as hydrophobia and biocompatibility. Even withAR coating, some level of reflection is imaged in some embodiments.Moreover, in embodiments of a capsule endoscope wherein AR coatings areeither not available or difficult to apply, no AR coatings are used.Instead, certain illuminator and/or camera geometries are used in someembodiments of a capsule endoscope 300, to ensure that internalreflections do not overlap with the image 305 on the image sensor I.

Specifically, as shown in FIG. 3, inner wall 303I and outer wall 303Eboth reflect light from short-range light source 302 back into capsuleendoscope 300. The reflections appear to have come from mirror images ofsource 302, namely virtual sources VS1 and VS2. The mirror images aredistorted in the horizontal direction in FIG. 3 by the cylindrical shapeof window 303 which is a portion of tubular wall 351 of endoscope 300.In the vertical direction in FIG. 3, the mirror images VS1 and VS2 arenot distorted unless the tubular wall of capsule 300 is not exactlycylindrical. For example, capsule endoscope 300 may be a prolatespheroid.

Tertiary reflections, e.g. optical paths with two reflections off theouter wall 303E and one off the inner wall 303I produce tertiary virtualimages that are at a farther distance from capsule endoscope 300 thanthe virtual sources VS1 and VS2. The tertiary virtual images are muchfainter than images VS1 and VS2 for the following reason. The energy ina reflected ray is reduced by 1/R^(n) after n reflections. For normalincidence, the reflectivity is typically 3-5% for polymers in air. Thereflectivity of unpolarized light increases with incident angle at asingle dielectric interface. Accordingly, the geometry of short-rangelight source position and objective lens position in some embodiments ofa capsule endoscope 300 are independent of whether or not tertiaryvirtual images are captured by camera 304.

Other reflective surfaces within capsule endoscope 300 may combine withsurfaces 303I and/or 303E to produce a significant secondary reflection.For example, if the body of camera 304 is reflective, then twoadditional virtual sources are produced further outside capsuleendoscope 300, than VS1 and VS2. Therefore the body of camera 304 insome embodiments of the invention has a low-reflectivity surface.

If virtual sources VS1 and VS2 lie within the FOV and the source 302emits into a wide range of angles, then the mirror images VS1 and VS2are captured in the image 305. If the virtual sources VS1 and VS2 lieoutside the FOV, as shown in FIG. 3, they are not imaged. Two exemplaryrays are shown in FIG. 3. One ray 307 reflects from the inner wall 303Itowards the pupil. The other ray 308 reflects from the outer wall 303Etoward the pupil P. VS1 and VS2 thus have a direct line of sight withthe pupil P in object space. However, these lines of sight are outsidethe FOV so the reflections VS1 and VS2 do not appear in the target image305.

In certain embodiments of endoscope 300, short-range source 302 is kepta certain distance (e.g. 4 mm) from the optical axis 306. The closer toa longitudinal axis 309 of capsule endoscope 300 that a source 302 is,the greater its distance from optical axis 306. Likewise, the greaterthe longitudinal FOV (shown in FIG. 3) the further that source 302 isplaced from optical axis 306. However, source positioning to keepreflections out of the image as shown in FIG. 3 has certain drawbacks.For example, the volume of the optical system of capsule endoscope 300increases as source 302 is forced farther from optical axis 306. Theheight of capsule endoscope 300 is reduced in some embodiments by usingsmall sources 302 (i.e. they occupy an annulus of small width) placedclose to window 303 of tubular wall 351. Small sources near the housingof endoscope 300 produce non-uniform illumination and “harsh” shadows.Accordingly, in some embodiments of capsule endoscope 300, large diffuselight sources with incident angles <60° relative to the illuminatedobject are used as short-range sources 302, to produce betterillumination of tissue.

Moreover, white sources with dimensions smaller than a few millimetersare used in some embodiments of capsule endoscope 300. Other embodimentsof capsule endoscope 300 use white LEDs that are formed by a blue orviolet LED encapsulated in an epoxy with phosphors. Also in certainembodiments of capsule endoscope 300, a die of the LED is located in areflective cavity along with an encapsulant, a positive electrode and anegative electrode. The reflective cavity is designed to efficientlyscatter light from the LED and phosphors, which both emitomnidirectionally, out from the encapsulant into a hemisphericdistribution. The die-attach and wirebond processes limit how small thecavity can be made relative to the die.

In some embodiments of capsule endoscope 300, the LED substrate isinsulating and two sets of wirebonds are included in the endoscope, toconnect the die to each electrode. In other embodiments of capsuleendoscope 300, the LED substrate is conductive, and the LED is bondedwith conductive epoxy or solder to one electrode and wirebonded to theother electrode. The last-described embodiments have a single wire bond,and result in a capsule endoscope 300 that is more compact than usingtwo sets of wirebonds. One illustrative embodiment uses as source 302,the following: EZBright290 available from Cree, Inc., 4600 SiliconDrive, Durham, N.C. 28703, USA Tel: +1.919.313.5300, www.cree.com.

In some embodiments, an endoscope 400 (FIG. 4) has a short-range lightsource 409 that includes a reflective cavity 401 and light emittingdiode (LED) 402. Cavity 401 directs light from LED 402 through anaperture 403, and out of endoscope 400 through a window 404 of thetubular wall. In these embodiments, the light source is positioned at apredetermined distance 405 (measured along a longitudinal axis which isnot shown in FIG. 4) from the optical axis 406 such that an aperture 407of a virtual source VS3 is outside the FOV.

In certain embodiments, a short-range light source is placed such thatone or more of its mirror images would be within the FOV, but for thepresence of internal walls (i.e. baffles) which are deliberatelypositioned between the light source and the window in the tubular wallto ensure that no line-of-sight exists from the pupil to the virtualimages. For example, in one such embodiment illustrated in FIG. 5, alight source S is higher than (i.e. closer to the optical axis than) thelight source 302 in FIG. 3 such that in FIG. 5 a portion of virtualimage VS4 is located within the FOV. The endoscope of FIG. 5 alsoincludes a baffle that is perpendicular to the tubular wall of theendoscope and located above the light source S. In the exampleillustrated in FIG. 5, the endoscope's tubular wall is orientedvertically, and a baffle 501 is oriented horizontally, mountedperipherally, and located in a plane between the objective and the lightsource S. Baffle 501 is formed as an annular wall in one illustrativeembodiment.

Baffle 501 reflects or absorbs incident rays, such as rays from source Sor rays reflected by window 503. In the embodiment of FIG. 5, a virtualimage 502 of the baffle blocks the line-of-sight between virtual imageVS4 and P within the FOV. Note that the baffle 501 creates a shadow onan object (e.g. tissue) which is illuminated outside the endoscope,which can be a disadvantage if captured in a diagnosable image. Notethat mirror 218 in FIG. 2E is a baffle because it blocks raysoriginating at source 205 from forming a virtual image that can becaptured by the camera.

In some embodiments, an aperture through which a source emits liespartially or fully within the FOV although the range of ray anglesemitted from the aperture is restricted as illustrated in FIG. 6.Specifically, in FIG. 6 a ray emitted from an aperture of source S isreflected from the window 601 at a point U. The projection of the rayonto a vertical plane containing U and the center of curvature C of thearc AUB (defined by the intersection of window 601 with a planecontaining U and parallel to optical axis PQ) at U makes an angle θ_(i)with the normal N to window 601. For a window 601 of a cylindricalshape, C is on the longitudinal axis (not shown in FIG. 6) of theendoscope 600. Let a be the angle between the normal and optical axisPQ. The reflected ray 607 (FIG. 6) does not enter pupil P ifθ_(i)>θ_(FOV)+α and this condition is satisfied in some embodiments ofendoscope 600, in accordance with the invention.

FIG. 7 illustrates an endoscope 700 of some embodiments including ashort-range source 709 formed by a LED 701 located within a cavity 702and mounted on a printed circuit board (PCB) 703. On the same PCB 703 ismounted an image sensor 704. A mirror 705 folds the optical axis anddirects image forming light onto sensor 705. Short-range source 709emits light into an input aperture A1 of an optical element 710 thatreduces the light's angular dispersion, i.e. an angular concentrator710. Light exits concentrator 710 through an output aperture A2.

In certain embodiments of endoscope 700, angular concentrator 710 limitsthe angular divergence in all directions to a half-angle of θ₂, and β isthe angle between the optical axis 706 of camera 711 and optical axis707 of the concentrator 710 and α is the angle (see FIG. 6) between ahousing surface normal N and the camera's optical axis 706. Suchembodiments ensure that internal reflections are outside the FOV bysatisfying the following relationship θ₂<β−θ_(FOV)−2α. Note that forseveral of these embodiments, β is in the range 45° to 135°. In someembodiments, window 712 is of cylindrical (or conical) shape, the pupilP is located on the longitudinal axis of the cylinder (or cone), andconcentrator 710 only limits the divergence in the radial direction(with respect to the window) to θ₂. These conditions are not met inother embodiments which limit the divergence in the tangential directionas well, although not necessarily to an angle as small as θ₂. Ingeneral, the divergence is limited such that θ_(i)>θ_(FOV)+α where θ_(i)is as defined above for all rays emitted from A2.

In a number of embodiments of an endoscope 700, the maximum angularconcentration in one dimension is defined from the radiance theorem as

$C_{m\; {ax}} = {\frac{\sin \; \theta_{1}}{\sin \; \theta_{2}} = \frac{a_{2}}{a_{1}}}$

Where θ₁ and θ₂ are the incident and exit angles, a₁ and a₂ are theinput and exit aperture diameters. The definition of C_(max) assumesthat the input and exit media are air. If the input aperture A1 ofconcentrator 710 is positioned directly on the encapsulant in cavity 702wherein LED 701 is mounted, only those rays that do not suffer totalinternal reflection enter the concentrator 710, and the input isconsidered to be these rays after refraction into free space. C_(max)quantifies the maximum possible reduction in angle with concentrator710, relative to without the concentrator. If θ₁=π/2 then

${\sin \; \theta_{2}} \geq {\frac{a_{1}}{a_{2}}.}$

FIG. 8 illustrates an endoscope 800 using a collimating lens 801 to forman angular concentrator 802 to reduce the angular divergence of lightfrom the short-range source 803. In FIG. 8, the concentration ratio islimited by the numerical aperture (NA) of lens 801. Since θ₁=π/2 much ofthe light from source 803 entering input A1 does not pass through lens801. In general, imaging systems, even complicated ones with multiplelenses, are not efficient angle concentrators (i.e. collimators) if thenumerical aperture (NA) required approaches one.

The concentration ratio of non-imaging concentrators, on the other hand,can approach C_(max). FIG. 9 illustrates an endoscope 900 using acompound parabolic concentrator (CPC) 902 as the angular concentrator.The sides of concentrator 902 have reflective surfaces 903 and 904.Depending on the embodiment, the body of concentrator 902 may be hollowas shown with mirrored surfaces 903 and 904 of sidewalls, oralternatively the body of the concentrator 902 is a dielectric with sidewalls whose surfaces 903 and 904 face each other and reflect light fromeach to the other, using total internal reflection (TIR). Hence someembodiments of endoscope 900 use two-dimensional CPCs, which are troughshaped, to approximate or even reach the maximum theoretical opticalconcentration. Variations of endoscope 900 in such embodiments includetruncated CPCs for which the height is reduced with only a small loss ofconcentration ratio. Certain embodiments of endoscope 900 use otherforms of concentrators, with planar sloped walls for example, achieve alower concentration ratio than the CPC but may still be useful.

The geometry of a cross section of a CPC 902 that is used in someembodiments of endoscope 900 is illustrated in FIG. 10. The inputaperture of CPC 902 is QQ′. The profile P′Q′ of one surface 903 ofconcentrator 902 is a portion of a parabola with focus at Q and axis atan angle γ to the axis Z of concentrator 902. Note that the LED 701 islocated on the axis Z directly facing input aperture QQ′. The length Lof concentrator 902 is chosen in some embodiments of endoscope 900 suchthat a skew ray from Q intersects the parabola at P′. The emissionhalf-angle is θ₂=γ. A truncated CPC reduces L and θ₂>γ. Details may befound in Nonimaging Optics, R. Winston, J. C. Minano, P. Benitez,Elsevier Academic Press, 2005, pp. 43-97 and 467-479 which isincorporated by reference herein in its entirety.

Some embodiments of an endoscope 900 include a cylindrical capsuleenclosing a panoramic imaging system with an annular CPC 1100 of thetype shown in FIG. 11. The cross-section of CPC 1100 in a planecontaining a radius is a two-dimensional CPC as illustrated in FIG. 10.CPC 1100 includes two halves, namely a first half 1101 and a second half1102 that are each glued to a ring (called “LED ring”). Each halfincludes two sidewalls that are physically attached to one another byradial spokes for structural support. For example, in FIG. 11, the firsthalf 1101 has an outer sidewall 1105 and an inner sidewall 1106 thatface each other, with spokes 1107-1109 providing support therebetween.Note that the two halves 1101 and 1102 of CPC 1100 are mirror images ofeach other, and for this reason when only the first half 1101 isdescribed below it is to be understood that second half 1102 has similardimensions, properties etc.

Note that in FIG. 11, outer sidewall 1105 surrounds inner sidewall 1106.Surface 1106R of inner sidewall 1106 faces surface 1105R of outersidewall 1105, and these two surfaces 1106R and 1105R reflect light suchthat it is deflected upwards. Sectioning sidewalls 1105 and 1106 along aradius of CPC 1100 results in a cross-section which forms a twodimensional CPC as illustrated in FIG. 9. Edges 1106E and 1105E ofrespective sidewalls 1106 and 1105 are adjacent to one another in abottom lateral plane. Accordingly, edges 1106E and 1105E together withedges of two adjacent spokes define a boundary of an input aperture ofCPC 1100 at its bottom surface (not shown in FIG. 11; see FIG. 12E).

In some embodiments, short-range sources in the form of LEDs arepositioned beneath each input aperture of CPC 1100 in a lead frame orpackage (not shown in FIG. 11; see FIG. 13). Specifically CPC 1100 has,on a bottom surface 1201 (FIG. 12A), several outward projections orbosses, such as bosses 1202 and 1203. The bosses are button shaped andare dimensioned and positioned to fit into and mate with correspondingdepressions or pockets in a lead frame wherein the LEDs are mounted.Moreover, an outer surface 1111 (which is a surface of outer sidewall1105) is made diffusing so that light from the input aperture diffuseslaterally out of surface 1111.

FIG. 12C illustrates, in a top elevation view, first half 1101 of CPC1100 of FIG. 11. FIG. 12B illustrates, in a cross-sectional view in thedirection A-A, in FIG. 12C, first half 1101 of annular CPC 1100 of FIG.11. FIG. 12D illustrates, in a side view in the direction D-D, in FIG.12C, the first half 1101 of FIG. 11. FIG. 12E illustrates, in a bottomelevation view, in the direction E-E, in FIG. 12C, first half 1101 ofFIG. 11. Note that portions 1208 of the bottom surface of CPC 1101 aremade diffusing so that light incident thereon is transmitted through CPC1101 and exits laterally through outer surface 1111 (FIG. 12A). Theheight of side walls 1105 and 1106 are 1.0 mm.

In some embodiments of an endoscope, CPC 1100 is formed as a moldedpolymer with a metal coating on the inside surfaces 1106R and 1105R toform mirrors. The walls of spokes 1107-1109 are sloped mirror-likeplanes that help to direct light upwardly. For example, spoke 1108 inFIG. 11 has spoke walls 1108A and 1108B that provide a degree ofconcentration in the tangential direction. Spokes 1107-1109 block raysfrom LEDs located underneath the input apertures of CPC 1100 with alarge tangential component that would otherwise lead to ghost images ofthe LEDs when internally reflected from the endoscope's housing, if thecamera pupils are not located on the longitudinal axis of the endoscope.Depending on the embodiment, spokes 1107-1109 may be absorbing insteadof reflecting although this reduces the efficiency in energy usage bythe endoscope.

FIG. 13 illustrates certain embodiments of an endoscope that includesCPC 1100 of the type described above in reference to FIGS. 11 and12A-12E, mounted on a lead frame 1300 such that LEDs supported thereinface input apertures in CPC 1100. In some embodiments, length L is onthe order of 1 mm. LED lead frame 1300 of the embodiments shown in FIG.13 is also ring shaped as illustrated in FIGS. 14A and 14B. Lead frame1300 contains multiple cavities 1401-1408 (FIG. 14A). Each of cavities1401-1408 holds an LED encapsulated therein with a phosphor in epoxy.For example, in FIG. 14A, cavity 1403 holds an LED 1409 that isconnected by a single bondwire 1410 to cathode lead 1411. Cavity 1403also holds an anode lead 1412. In some embodiments, the walls of eachcavity of lead frame 1300 are white diffuse reflectors.

LED lead frame 1300 also has a number of pockets, such as pocket 1415(FIG. 14A) that mates with and holds button shaped bosses of CPC 1100when they are press-fit or otherwise inserted. Note that in someembodiments the just-described bosses and pockets are reversed inposition, i.e. the CPC has pockets and the LED lead frame has bosses.Also depending on the embodiment, other structures may or may not beused to physically join LED lead frame 1300 and CPC 1100 to one another.

In the embodiment shown in FIG. 13, the LED lead frame 1300 has cavity1403 with an aperture A3 that is located only partially under inputaperture A1 of the CPC 1100. Specifically, a portion of aperture A3 ofcavity 1403 is covered by a surface 1208 of outer sidewall 1105 of CPC1100. In one illustrative example, A3 is 0.9 mm and A1 is 0.5 mm. Hence,light from LED 1409 enters sidewall 1105 through surface 1208. Surface1208 of some embodiments is diffusive as shown in FIG. 12E. Any suchlight which has entered sidewall 1105 then passes laterally throughouter surface 1111 to a scene outside the endoscope, if the CPC's outersidewall is transparent. A portion of this light which exits surface1111 is reflected by the reflective cavity surface of CPC 1100.

Surface 1111 at the outer rim of CPC 1100 has a rough surface so thatlight exiting the endoscope from surface 1111 is scattered and diffused,which is used to illuminate objects at a short to intermediate distancefrom the endoscope (see FIGS. 2I, 2J and 2K). In the endoscope structureillustrated in FIG. 13, the same LED provides short-range light toilluminate objects at a short or intermediate distance from theendoscope by diffuse illumination through surface 1111, and alsoprovides additional short-range light via aperture A2 for use inradially illuminating objects touching or a short distance from theendoscope. For example, an annular mirror (see mirror 218 in FIGS. 2E,17 and 18) reflects a portion of light that exits aperture A2, out of awindow of a tubular wall of the endoscope, and simultaneously anotherportion of the light exits out of the window directly from aperture A2.

In some embodiments, a CPC of an endoscope has an input aperture A1 thatcoincides with the aperture A3 of a short-range source, wherein there isno overlap (or negligible overlap) of the CPC's outer sidewall with thelead frame's cavity as shown in FIG. 15. Also, in certain embodiments, aCPC 1600 in an endoscope is made of a dielectric material as shown inFIG. 16, although the concentration ratio is reduced for a given lengthL of CPC due to refraction at the output aperture.

Some embodiments of an endoscope of the type described herein providemulti-modal illumination in accordance with the invention, by usingdifferent amounts of energy to illuminate tissue, depending on thedistance of the tissue. Specifically as illustrated in FIG. 17 on theright side, mucosa surface 1701 at points F and G which is close to(e.g. <5 mm) or touching endoscope 1700, is illuminated by lightemerging from CPC 1100, both directly and after reflection from annularreflector 218. In the illustrative embodiment shown in FIG. 17,reflector 218 enables light from an emitter in short-range source 1703to reach an illumination region of the endoscope from both sides of thefield of view, thereby to illuminate tissue surface 1701 more uniformlyin an image to be diagnosed, as compared to short-range illuminationfrom only one side of the field of view.

Additionally, a tissue surface 1701 located at point H which is incontact with endoscope 1700 is also illuminated by light emerging fromsurface 1111 which light entered CPC 1100 through a bottom surface asdescribed above, and is reflected by a convex surface in CPC 1100. Astissue surface 1701 is in contact with endoscope 1700, point H isoutside the FOV of the camera. However, as the distance increases, pointH falls within the FOV. Accordingly, endoscope 1700 uses a minimumamount of energy, e.g. by using primarily just a single LED withinshort-range source 1703 in the direction towards the right of FIG. 17.

Note that endoscope 1700 of these embodiments includes an additional LEDused for long-range source 1704 that, when turned on, also provideslight in the same radial direction, i.e. towards the right of FIG. 17.Long-range source 1704 is positioned longitudinally offset from theobjective's optical axis, e.g. positioned behind mirror 218 which actsas a baffle. Note that there is little or no overlap between thelong-range illumination region on the endoscope's tubular wall (close topoint E in FIG. 17) lit up by light source 1704, and the above-describedshort-range illumination region lit up by light source 1703. The area oflong-range illumination region lit up by light source 1704 is severaltimes and in some cases an order of magnitude, smaller than thecorresponding area of short-range illumination region lit up by lightsource 1703.

Endoscope 1700 increases the radiant energy generated by the long-rangelight source 1704 as the distance of the tissue to be imaged increases.Using long-range light source 1704 simultaneously with short-range lightsource 1701 provides sufficient illumination to image mucosa 1701 thatis located far away (e.g. ˜20 mm away). For example, points A-D shown onthe left side of FIG. 17 are illuminated by turning on both lightsources 1706 and 1707.

Use of both light sources 1706 and 1707 does use up a maximum amount ofenergy (relative to use of just one source 1706), although such useprovides better images which enable a more thorough diagnosis of a bodycavity, such as a gastrointestinal tract. The energy generated bymultiple light sources 1703 and 1704 to illuminate radially in a givendirection may be scaled appropriately, to illuminate tissue located atintermediate distance(s) as described above in reference to FIG. 2I.Accordingly, endoscope 1700 in some embodiments of the inventionoperates multi-modally, specifically in a minimum energy mode, a maximumenergy mode and one or more intermediate energy modes. For certain bodycavities, such as a small intestine, endoscope 1700 of these embodimentsoperates continuously in a minimal mode, by turning on only theshort-range source, e.g. source 1703 (i.e. the long-range source is keptturned off).

Note that endoscope 1700 of FIG. 17 incorporates four objectives withoptical axes spaced 90° apart, although only two lenses 1711 and 1712that are oppositely directed are shown in FIG. 17. In this embodiment,eight LEDs are arrayed in a ring under an annular truncated CPC 1100.The eight LEDs emit out the outer surface 1111 of CPC 1100 and alsothrough the top of the CPC apertures A2 (not labeled in FIG. 17). Someof the light from aperture A2 is reflected down and out of the endoscope1700 by annular mirror 218 located above the imaging region. In FIG. 17,the angle of the mirror 218 relative to the optical axis is chosen suchthat the reflected light satisfies the relationship θ_(r)<θ₂ where θ₂ isthe maximum angle of light exiting the CPC cavity in the radialdirection and θ_(r) is the angle of a ray reflected from the annularmirror relative to an inner or outer surface of the tubular wall.

Note that the embodiment illustrated in FIG. 18 is similar or identicalto the embodiment described above in reference to FIG. 17 except that inFIG. 18 the annular mirror has a convex cross section. The convexcross-section mirror is used because the relationship θ_(r)<θ₂ need notbe satisfied for all reflected rays. The shape of the mirror'sreflective surface is empirically chosen, to optimize uniformity ofillumination. In one illustrative embodiment, a convex section of thereflective surface has a radius of curvature close to 10 mm.

In the embodiments of FIGS. 17 and 18, the outer rim of the CPC issufficiently below the optical axis so that virtual images of it areoutside the FOV. Thus, no single-reflection ghost images of it will bevisible. The light emitted from the cavity of the CPC is restricted inangle so that reflections will miss the camera pupil. Additionally, asnoted above, in order to illuminate distant objects, set of LEDs isarrayed around the endoscope, above the mirror. The output apertures ofthese LEDs are sufficiently above the optical axis so thatsingle-reflection ghost images are outside the FOV. If the mucosa isclose, these LEDs primarily illuminate region E which is outside theFOV, and for this reason the LEDs need not be turned on. If the mucosais at an intermediate distance, the top LED illuminates primarily thetop half (D) of the mucosa while light emitted from the side of the CPCprimarily illuminates the bottom half (C). If the mucosa is fartheraway, the top LED effectively illuminates the entire FOV (I, J, K).

In some embodiments, the lower LEDs 217 (FIG. 2E) do shine light onobjects within the capsule, such as parts of the camera, whose mirrorimages are within the FOV. To minimize ghost images, these objects havelow reflectivity. Also, the angle of reflection from these objects iscontrolled by making the surfaces specular and choosing their anglesrelative to incident light appropriately. In several embodiments, thesestrategies reduce but not eliminate ghosting. Thus, certain embodimentslimit the intensity of the lower (also called “bottom”) LEDs 217. As themucosa moves further from the endoscope, more illumination light isprovided. However, the additional light is provided from the top LEDs205 which direct all of their light outside the capsule 200. Theillumination, and hence image exposure, is controlled by varying theintensity of the LEDs 205 and 217 in an attempt to make illuminationuniform as described below. The flux from the bottom LEDs 217 is limitedin some embodiments to a maximum value that provides sufficientillumination when the mucosa is close but not so high as to produceobjectionable ghosting.

Numerous modifications and adaptations of the embodiments describedherein will become apparent to the skilled artisan in view of thisdisclosure.

For example, although some embodiments of the invention use radialillumination, other embodiments use longitudinal illumination with twolight sources that are mounted adjacent to a dome-shaped end to provideillumination in a longitudinal direction. Specifically, an endoscope1900 has a dome-shaped end 1903 through which illumination is providedby a first set of LEDs (e.g. four LEDs) mounted in a common plane(perpendicular to a longitudinal axis) and labeled as “LED A” in FIG.19. The first set of LEDs A are used to provide short-range illuminationwhen tissue is close to or in contact with endoscope 1900. In theembodiment of FIG. 19, endoscope 1900 has a second set of LEDs (e.g.four LEDs) which are labeled as “LED B” in FIG. 19. The second set ofLEDs B are used to provide long-range illumination when tissue is at anintermediate distance or even far away, at a predefined outer limit ofthe endoscope. Hence, depending on the distance between tissue to beimaged and endoscope 1900, the first set of LEDs A is used by itself orin combination with the second set of LEDs B (as illustrated in FIGS.2I, 2J and 2K) to provide illumination necessary to generate diagnosableimages in endoscope 1900.

In the embodiment illustrated in FIG. 19, light from the first set ofLEDs A exits dome-shaped end 1903 longitudinally (rather than laterallyas noted above for other embodiments) via an aperture 1905 defined by acylindrical wall 1901. Wall 1901 surrounds LEDs A so that light from thefirst set is directed out of aperture 1905. Moreover, LEDs B are mountedfarther away (in radial distance from a longitudinal axis of endoscope1900) than LEDs A. In the embodiment illustrated in FIG. 19, LEDs Bsurround the wall 1901 and are mounted facing a diffuser 1902. Diffuser1902 may be, for example, a Fresnel optic, hologram or other opticalelement that diffuses the light from LED B. Accordingly, endoscope 1900uses LEDs A primarily to illuminate close and distant objects and usesLEDs B primarily to illuminate distant objects.

Moreover, instead of light other embodiments use electromagneticradiation that is invisible to the human eye, e.g. ultra-violet orinfra-red ranges. Hence, numerous modifications and adaptations of theembodiments described herein are encompassed by the scope of theinvention.

FIG. 25 illustrates dimensions, in millimeters, of an exemplary annularmirror 218 having a convex reflecting surface in some embodiments of theinvention. Moreover, FIG. 26 also illustrates dimensions, inmillimeters, of an endoscope shaped as a capsule in some embodiments ofthe invention, which contain the annular mirror 218 of FIG. 25.

Referring to FIG. 13, an aperture A3 of lead frame 1300 is located onlypartially under input aperture A1 of the CPC 1100. CPC 1100 has anadditional input aperture A5 (“second input aperture”), which is inaddition to the above-discussed input aperture A1 (“first inputaperture”). Apertures A1 and A5 together form an input aperture A4through which all light is received by CPC 1100 from LED 1409.Specifically, rays 1301 and 1302 from LED 1409 enter CPC 1100 via thesecond input aperture A5 through surface 1208 of CPC 1100. Ray 1301 isrefracted within sidewall 1105 of CPC 1100 on entry at surface 1208 andthen reflected by a layer 1309 formed on sidewall 1105. The layer 1309has two surfaces, namely a convex surface 1309X which is formed onsidewall 1105 located opposite to outer surface 1111, and a concavesurface which forms an inside surface 1105R of CPC 1100.

More specifically, as shown in FIG. 13, surfaces 1309X and 1105R are twosides of a layer 1309 that constitutes a portion of CPC 1100, inaddition to sidewall 1105. In one illustrative example, surfaces 1309Xand 1105R of layer 1309 are within 100 microns of each other, i.e. thelayer 1309 is 100 microns thick. Surface 1309X of layer 1309 (shown as aheavy black line in FIG. 13) reflects at least some of the incidentillumination towards outer surface 1111, as illustrated by reflection ofray 1301 at point 1321. Note that CPC 1100 additionally includes anotherlayer 1399 (shown in FIG. 13 as another heavy black line) whose concavesurface forms another inside surface 1106R. Depending on the embodiment,either or both of layers 1309 and 1399 may be formed as either (a) asingle metal layer (e.g. aluminum or silver) or (b) a multi-layeredstack of dielectric layer(s) and/or metal layer(s).

Illumination from LED 1409 which is incident from within sidewall 1105,on outer surface 1111 (FIG. 13) diffuses out from CPC 1100 through anoutput aperture A6 as light portions 1311 and 1312, e.g. respectivelyresulting from rays 1301 and 1302. Specifically, as shown in FIG. 13, aray 1302 also enters sidewall 1105 via the second input aperture A5,although its angle of incidence and its angle of refraction, are of suchvalues that this ray 1302 is not reflected by surface 1105R ofreflective layer 1309. Instead, ray 1302 is refracted at surface 1208and is transmitted to and directly incident on surface 1111 at outputaperture A6 without reflection, and thereafter diffuses out of sidewall1105 as shown in FIG. 13 as light portion 1312. Accordingly, two lightportions 1311 and 1312 are redirected towards aperture A6 by refractionand either direct transmission or transmission and reflection by CPC1100, so as to be incident on bottom spot 210C in FIG. 2B (see intensitydistribution 219C in FIG. 2E) which constitutes one fraction formed bybeam 208C (FIG. 2D). As noted above, bottom spot 210C has area less than50% of the total area of short-range illumination region 210 of acapsule endoscope 200.

As noted above, one light portion 1311 (FIG. 13) is included in aportion of the light fraction (“first fraction”) emitted by LED 1409that is reflected by surface 1309X of the layer 1309. Another surface1105R of layer 1309 receives a portion of another fraction (“secondfraction”) of light emitted by LED 1409 which enters first inputaperture A1 (illustrated by ray 1303). Surface 1105R reflects most ofthis portion through output aperture A2, towards another opticalelement, namely mirror 218 as illustrated by ray 1313 (see FIG. 13).Accordingly, CPC 1100 of FIG. 13 has two output apertures namelyapertures A2 and A6, and these two output apertures are orientedlaterally relative to one another (e.g. oriented at 90 degrees).

Note that in the embodiment illustrated in FIG. 13, another portion of asecond light fraction from LED 1409 which enters the CPC 1100 at firstinput aperture A1, is illustrated by a ray 1304 that reaches anotherinside surface 1106R of another reflective layer 1399 of CPC 1100. Lightreflected by inside surface 1106R also exits the CPC 1100 through outputaperture A2, e.g. as shown by ray 1314. Depending on the angle ofincidence, ray 1314 may be reflected by surface 1106R at such a smallangle relative to a longitudinal axis of the endoscope that this ray1314 also reaches mirror 218. Mirror 218 may also receive anotherportion of the second light fraction that is transmitted through CPC1100 without reflection, as illustrated by ray 1316. As noted above,rays reaching mirror 218 from aperture A2 constitute a beam 208B whichis reflected by mirror 218 toward a top spot 210B as shown in FIG. 2B(see intensity distribution 219A in FIG. 2E).

Depending on an offset distance 1398 between LED 1409 and CPC 1100 (e.g.measured from a center of the CPC cross-section), a third light fractionas illustrated by ray 1319 is reflected by surface 1106R at an anglesufficient large relative to the longitudinal axis such that the raydirectly exits the endoscope without reflection, e.g. via a middle spot210A of illumination region 210 in FIG. 2C (see intensity distribution219B in FIG. 2E). Also included in the third light fraction is anotherray 1315 which is also directly transmitted through CPC 1100 withoutreflection therein. As noted above, the third light fraction forms abeam 208A which exits the endoscope housing at a middle spot 210A.

Note that the offset distance 1398 shown in FIG. 13 determines therelative proportion of light transmitted through the two input aperturesof the CPC, specifically A1 and A5. If offset distance 1398 is increasedthen the amount of light through input aperture A5 increase relative toinput aperture A1. Depending on the embodiment, offset distance 1398 canbe a predetermined fraction (e.g. two-thirds, half, one-third, or evenone-fifth) of the width of input aperture A1. In one illustrativeembodiment, offset distance 1398 is one half of width of input apertureA1 which results in about one half of light from the LED 1409 enteringaperture A5 and exiting sidewall 1105 through a non-imaging region ofthe housing, e.g. region 210C and another half of the light enteringaperture A1 and exiting through an imaging region 212 of the housing(see FIG. 2A).

In embodiments of the type illustrated in FIG. 13, LED 1409 and aphosphor in epoxy within cavity 1403 together form a source of light,wherein all light from this source is emitted on one side (e.g. bottomside) of a plane 1397. Note that CPC 1100 (which is an optical element)is located on the other side (e.g. top side) of the plane 1397.Additionally, as illustrated in FIG. 14, this source includes a pair ofterminals represented by cathode lead 1411 and anode lead 1412 and acurrent passing therebetween causes the light emitting diode to generatelight. As a portion of the generated light directly emerges fromaperture A3 (FIG. 13), LED 1409 is an emitter for this portion. Anotherportion of the generated light is incident on the phosphor which absorbsthe incident light and uses the energy therefrom to generate light in adifferent wavelength, and hence the phosphor is another emitter. Notethat although a short-range illumination source is illustrated in FIGS.13 and 14, in some embodiments both types of sources (long-range andshort-range) 205 and 206 that are enclosed within a housing of anendoscope are identical to one another. Specifically, multiple copies ofthe same LED are used as a long-range source 205 and also as ashort-range source 206.

Referring to FIGS. 4 and 5 as described above, only one virtual sourceis illustrated in each figure to aid in conceptual understanding. Incapsule endoscopes of most embodiments, there are at least two virtualsources as shown in FIG. 3. Specifically, reflections from an innersurface (not labeled in FIG. 4) and from an external surface (also notlabeled) of window 404 result in two virtual sources, of which only avirtual source formed by reflection from the external surface of theendoscope's window is shown in FIG. 4. Similarly, there are tworeflections from the two surfaces of window 503, of which only areflection by the external surface is shown in FIG. 5.

Hence, the number of virtual sources formed by a corresponding number ofreflections from a capsule endoscope's window in turn corresponds to thenumber of surfaces in the window. Specifically, in several embodiments awindow in fact includes multiple interfaces (e.g. 3 interfaces asillustrated in FIG. 27), in which case orientation of the multipleinterfaces and materials used to form layers in the endoscope's windowdetermine the actual paths of transmitted and reflected rays resultingfrom an illumination ray. In the illustration of FIG. 27, a rayoriginating from source 302 is reflected at each of surfaces 303I, 303Eand 303N, and such reflections form three virtual sources VS1, VS2 andVS3.

Accordingly, in several embodiments, illumination regions 210 and 211and imaging region 212 (illustrated in FIGS. 2A and 28A) are all formedon an inner surface of the housing of endoscope 200. In otherembodiments all these regions 210-212 are formed on an outer surface ofthe housing of endoscope 200. And in still other embodiments all theseregions 210-212 are formed on an intermediate surface (i.e. aninterface) within the housing of endoscope 200.

Regardless of the number of surfaces of a window in a capsule endoscopeof some embodiments, imaging of the corresponding virtual sources in thecamera is avoided by one or more of the above-described methods, e.g. bypositioning the source sufficiently spaced apart (in the longitudinaldirection) from the optical axis of the camera as illustrated in FIG. 3or by shielding as illustrated in FIGS. 4 and 5. Furthermore, note thatalthough only a single light source is illustrated in each of FIGS. 3-5and 28, several embodiments use multiple light sources and imaging oftheir respective virtual sources is also avoided or minimized asdescribed above.

Moreover, similar to FIG. 2C discussed above, FIG. 28A illustrates wall201M of capsule-shaped endoscope 200 of some embodiments having animaging region 212 overlapping a short-range illumination region 210through which light is emitted from endoscope 200 for short-rangeillumination. Wall 201M in FIG. 28A also has a long-range illuminationregion 211 through which light is emitted from endoscope 200 forlong-range illumination. Note that in FIG. 28A, imaging region 212 doesnot overlap the long-range illumination region 211. The just-describedabsence of overlap between imaging region 212 and long-rangeillumination region 211 enables operation of a long-range illuminationsource at a significantly higher intensity (e.g. an order of magnitudehigher) relative to the intensity of a short-range illumination source,without resulting in an unduly bright region within the image formedwithin a camera of endoscope 200, which is in contrast to capture ofpoint 2805 shown in FIGS. 28B and 28D (discussed below).

In certain alternative embodiments, imaging region 212 overlapslong-range illumination region 211, as illustrated by point 2805 inFIGS. 28B and 28D. In several such embodiments, there is no overlapbetween the short-range illumination region 210 and the long-rangeillumination region 211 (FIG. 2B). In these embodiments, imaging region212 (FIG. 2B) also contains a point 2804 that lies in short-rangeillumination region 210 but does not lie in the long-range illuminationregion 211. Point 2804 can be any point in the imaging region 212, e.g.an intersection of an optical axis of the camera with an outer surfaceof the housing. In some embodiments, all three regions 210, 211 and 212overlap one another as illustrated by point 2805 in FIG. 28D. Note thatoverlap of the type illustrated in FIGS. 28B and 28D typically resultsin an exceptionally bright region in an image, and the bright region iscropped as discussed above, and in the next paragraph. Note thatembodiments that use other types of cameras (such as a panoramic camera)also satisfy one or more of the above-described relationship, e.g. seepoint 2804 in FIGS. 31 and 32.

In several embodiments of the type shown in FIG. 28B, an image formedwithin the camera includes an unduly bright region, caused by reflectionof that fraction of light exiting the endoscope which originates in along-range illumination source. Hence, in some embodiments of the typeshown in FIG. 28B, image data representing a diagnosable image at aspecific location in a gastrointestinal tract is obtained by excluding(i.e. discarding) certain data (“additional data”) which represents theunduly bright region. Specifically, depending on the embodiment, adiagnosable image can be generated in different ways, such as (a)inherent cropping by appropriate design of hardware within theendoscope's camera e.g. by including therein a sensor sized andpositioned appropriately to not sense the additional data and/or (b)cropping performed by appropriately programming firmware and/or softwareexecuted by a processor included within endoscope 200, and/or (c)cropping performed by imaging application software executed by anexternal computer that receives a combination of image data andadditional data from the transmitter (such as Microsoft® Office PictureManager available from Microsoft Corporation), to generate image data(by excluding the additional data), store the image data in thecomputer's memory, and display a diagnosable image to a physician (e.g.a gastroenterologist) for use in diagnosing diseases.

The just-described cropping is not required if positions of the twosources relative to the camera are such that imaging region 212 does notoverlap the long-range illumination region 211 as noted above inreference to FIG. 28A. Note that the just-described lack of overlap isfurther illustrated in other embodiments of the type shown in FIG. 28Cwherein short-range illumination region 210 overlaps the long-rangeillumination region 211. In the embodiments of FIG. 28C, imaging region212 contains point 2804 that lies in short-range illumination region 210but does not lie in long-range illumination region 211. Moreover,certain embodiments that perform cropping as described above have thetwo illumination regions and the imaging region, i.e. all three regionsoverlap one another as shown in FIG. 28D. As noted above, in embodimentsof the type illustrated in FIG. 28D, point 2805 is located within eachof the three regions 210, 211 and 212. Note that in the embodiments ofFIGS. 28D and 28A, imaging region 212 contains point 2804 that lies inshort-range illumination region 210 but does not lie in long-rangeillumination region 211. Note that the just-described condition issatisfied in each of the four types of embodiments illustrated in FIGS.28A-28D.

In some embodiments, a number of imaging regions that are adjacent,overlap each other, as illustrated by overlap regions 285A and 285B inFIG. 28E. Specifically, overlap region 285A results from overlap of thetwo adjacent imaging regions 282A and 282Z, and overlap region 285Bresults from overlap of the two adjacent imaging regions 282A and 282B.As noted elsewhere herein, a set of sensors (e.g. two sensors 3401 and3402 illustrated in FIG. 34) are located within a central region ofendoscope 200, and each sensor in the set receives and forms a portionof an image of light reflected by tissue and reaching a correspondingone of the respective imaging regions 282A-282Z shown in FIG. 28E.Hence, in several embodiments, data generated by a set of sensors issupplied in whole or in part (after optional cropping by a processor) toa transmitter that in turn transmits image data representing adiagnosable image to an external device.

Note that although a set of two sensors is illustrated in FIG. 34 forsome embodiments of an endoscope, other embodiments use fewer or moresensors in a set coupled to the transmitter (e.g. one embodiment uses aset of one sensor). In an illustrative embodiment, a sensor chip in anendoscope has a pixel array to record four portions of an image fromfour objectives in four regions thereof, as illustrated by Q1-Q4 in FIG.2O and FIG. 20, and the sensor chip supplies the image data capturedtherein to a transmitter. As will be readily apparent to the skilledartisan in view of this disclosure, other embodiments do not use fourregions of a single monolithic sensor chip as shown in FIG. 2O and FIG.20 and instead use a set of four sensors, and image data resulting fromoperation of the set of four sensors at a single location is supplied tothe transmitter for generation of a diagnosable image by an externalcomputer.

In embodiments of the type illustrated in FIG. 28E, the light reachingoverlap region 285A is sensed by two sensors for imaging regions 282Zand 282A respectively. Similarly, there are two sensors within endoscope200 which receive light that has been reflected by tissue of thegastrointestinal tract and reaches overlap region 285B. Due to overlaps,a region 282 (FIG. 28F) formed by a union of all imaging regions282A-282Z of an endoscope is a continuous band (i.e. union region 282)around the endoscope's tubular wall as illustrated in FIG. 28I.Accordingly, imaging region 282 of endoscope 200 is defined by anintersection of a surface (e.g. outer surface) of the housing withelectromagnetic radiation (“imaging illumination”) entering the housingand being captured in image data supplied by the set of sensors to atransmitter. As noted elsewhere herein, a computer that eventuallyreceives the image data is appropriately programmed to generatetherefrom a panoramic 360° image that is displayed to a physician.

In embodiments of the type illustrated in FIG. 28E, ghosting isprevented by positioning a long-range illumination source within theendoscope housing such that a majority of light exiting the housingwhich originates from the long-range illumination source passes througha region 281A of the housing (“long-range illumination region”).Long-range illumination region 281A of such embodiments (FIG. 28E) doesnot overlap any of imaging regions 282A-282Z (and therefore does notoverlap union region 282 of FIG. 28F). Specifically, in someembodiments, long-range illumination region 281A is separated (in thedirection of the longitudinal axis of endoscope 200) from acorresponding imaging region 282A. Hence, in the embodiment of FIG. 28E,there is no overlap between regions 281A and 282A due to a verticalseparation distance 200V therebetween, which has a positive value.Furthermore, note that regions 281A and 282A may be also offset in thecircumferential direction. Specifically, in the embodiment shown in FIG.28E, a center 282C of region 282A is separated by circumferentialdistance 200H from a center 281C of region 281.

However, as illustrated in FIG. 28G, in many embodiments, due toconstraints on the size of a capsule that is small enough to beswallowable, the vertical separation distance 200V has a negative value,which results in an overlap region 286A (FIG. 28H) between regions 281Aand 282A. Due to a positive value for circumferential distance 200H (notlabeled in FIG. 28G, see FIG. 28E), the long-range illumination region281A also overlaps an adjacent imaging region 282B, as shown in FIG. 28Hby the overlap region 286B. However, in other embodiments,circumferential distance 200H (FIG. 28E) is sufficiently small toeliminate any overlap between long-range illumination region 281A andadjacent imaging region 282B.

FIG. 28H shows a non-overlapping illumination region 286C which is aremainder of region 281A left by disregarding overlap regions 286A and286B. Specifically, regions 286A, 286B and 286C together form long-rangeillumination region 281A. Overlap regions 286A and 286B (if any) arekept small, within conformance with space constraints of a swallowablecapsule, to minimize ghosting resulting from light originating at thesource, being reflected by an inner surface and reaching the camera(s)without ever exiting the capsule endoscope 200. Hence, several capsuleendoscopes of the type described herein have at least 50% of (e.g. amajority of, or most of) light, which is emitted by a single long-rangelight source and which exits through long-range illumination region 281Aactually exit capsule endoscope 200 through non-overlapping region 286C.Specifically, in several embodiments, non-overlapping region 286C isseveral times larger than overlap regions 286A and 2868.

In many embodiments, a majority of light, which exits endoscope 200 andoriginates in a long-range light source, does not exit through unionregion 282. To re-iterate, in some embodiments, the light, which exitsthrough overlapping regions 286A and 286B, is less than 50% of lightfrom any long-range light source that exits the housing to reach outsidethe endoscope 200. At least a portion of the just-described majority isincident on the gastrointestinal tract, gets reflected therefrom, andenters endoscope 200 through union region 282.

Note that in certain specific embodiments of capsule endoscope 200,wherein each long-range illumination region 281A is sufficiently alignedwith a corresponding imaging region 282A, almost all of the light (e.g.90% or more) which exits capsule endoscope 200 through long-rangeillumination region 281A is emitted by a single long-range light sourcecorresponding thereto. Hence, in the just-described embodiments, only anegligible amount of stray light from other light sources (e.g. adjacentsources) within the capsule endoscope exits through each long-rangeillumination region.

As noted above in reference to FIG. 2C, many embodiments of a capsuleendoscope also have one or more short-range light illumination region(s)210, which may correspond to (but are not necessarily aligned with)either or both of imaging region 212 and/or long-range illuminationregion 211, depending on the embodiment. Specifically, as shown in FIGS.28K and 28L for embodiments that correspond to FIGS. 28E and 28Grespectively described above, a short-range illumination region 283Aoverlaps imaging region 282A in overlap region 289A. Overlap region 289Ahas an area which constitutes more than 50% of the area of imagingregion 282A.

Hence, more than 50% of light which exits some embodiments of a capsuleendoscope through imaging region 282A, actually exits through overlapregion 289A. Accordingly, in certain embodiments, at least 50% of light(e.g. a majority or most of light) emitted by a short-range light sourceand exiting the housing of a capsule endoscope, actually exits throughunion region 282. In several such embodiments, multiple short-rangeillumination regions also overlap one another, to form a continuous band283 around the circumference of a tubular wall (which is shown unrolledfor illustration purposes in FIGS. 28I and 28J, as noted above).

Furthermore, as shown in FIGS. 28A-28D, the area of a short-rangeillumination region 210 is typically several times e.g. 2 times, 3times, 4 times or even 5 times larger than the area of a long-rangeillumination region 211. Also as illustrated in FIGS. 28K and 28L, thearea of illumination region 283A is 3 or 4 times larger than the area ofillumination region 281A, In several such embodiments, the two types oflight sources included in a capsule endoscope, namely a short-rangelight source and a long-range light source, each include emitters thatare identical to one another, i.e. the emitters are implemented usingmultiple copies of a single product (e.g. LED), and accordingly have thesame ratings as one another. However, as noted above, the short-rangelight sources of a capsule endoscope in accordance with the inventioninclude one or more optical devices to split light from the emittertherein, into multiple fractions and/or portions and/or parts that areinitially redirected by the optical device(s) along different paths butfinally brought together at the housing, to form an illumination region210 which is several times larger than illumination region 211 formed bylight incident directly on the housing from an emitter in a long-rangelight source.

Several embodiments differ from the above-described embodimentsillustrated in FIGS. 6 and 7, wherein several differences areillustrated in FIGS. 29A and 29B and/or described below. In embodimentsof the type illustrated in FIGS. 29A and 29B, an illumination ray 2901emitted from source aperture S is reflected from an inner surface 2902of window 2903 in a tubular wall of the housing of the endoscope.Specifically, point U is at the intersection of the incident ray 2901and the reflected ray 2904. In FIG. 29A, the ray 2901 is collinear witha line 2907 and reflects from inner surface 2902 at point U on innersurface 2902 to form reflected ray 2904 along a line 2908. Note that inFIG. 29A, V is a plane formed by the three points S, U and P where P iswithin the pupil of the camera. In some embodiments, plane V in FIGS.29A and 29B is vertical, i.e. coincident with the plane of the paper inFIG. 29A, and therefore points U, P, S lie in plane V as do ray 2904 andnormal line N.

Accordingly, in the just-described embodiments, plane V is alongitudinal plane coincident with the plane of the paper on which FIG.29A is drawn. This longitudinal plane V passes through theabove-described point U and through a point C, wherein C is the centerof curvature of an arc AUB (FIG. 6). The just described lateral plane isparallel to the optical axis PQ (FIGS. 6 and 29A) and passes through theintersection point U. The lateral plane and the longitudinal plane areperpendicular to one another in embodiments of the type illustrated inFIG. 29A. In other embodiments, plane V is not vertical and insteadpoints P and S in FIG. 29A are projections in a vertical plane that iscoincident with the plane of the paper in which normal line N lies.Accordingly, the geometry shown in FIG. 29A is similar to the geometryshown in FIG. 6 except that in FIG. 29A, the angle of incidence of ray2901 is θ_(i) whereas in FIG. 6 θ_(i) is the projection of the angle ofincidence on to a vertical plane containing C and U, i.e. the verticalplane projection of ray SU in FIG. 6.

Referring to FIG. 29B, incident illumination ray 2901 is first refractedat the inner surface 2902 into window 2903, reflects from outer surface2905 as ray 2906, and then refracts at inner surface 2902 to becomereflected ray 2904. In FIG. 29B, point U is within the window 2903, andN is a line that bisects an angle formed by incident ray 2901 andreflected ray 2902. If inner surface 2902 and outer surface 2905 areparallel to one another, then line N is normal to both surfaces 2902 and2905, at point U.

Referring to both FIGS. 29A and 29B, an angle of incidence of ray 2901at inner surface 2902 is θ_(i) as discussed above. Also in both FIGS.29A and 29B, illumination ray 2901 and line N together define theabove-described plane V. In several embodiments, there exists a set ofimage forming rays entering the pupil P of an endoscope's camera withinthe field of view (FOV) which lie in plane V and which either passthrough point U (FIG. 29A) or appear to pass through point U when viewedfrom inside the endoscope (FIG. 29B). Specifically, consider a ray UPgoing from point U to point P, with P within the pupil, that makes anangle σ with line N. The reflection of incident illumination ray 2901intersects point P if θ_(i)=σ.

Hence in several embodiments, the illumination rays from source S arerestricted in angle such that θ_(i)>σ for a majority of pairs of rays(such as one pair 2901 and 2904, and another pair 2911 and 2914) in allplanes V of FIGS. 29A and 29B, to reduce or eliminate a ghost of thesource S (i.e. a virtual source) from an image captured by the camera.For example, in several embodiments source S is positioned, byexperiment, at a location that is chosen to be at an angle θ_(i)relative to the optical axis of the camera, selected to be sufficientlylarger than angle σ (e.g. 1° larger), so as to avoid ghosting in thegeometry illustrated in FIGS. 25 and 26.

As described above, image data representing a diagnosable image issupplied to a transmitter of the endoscope. A transmitter as used hereinincludes a wireless transmitter (e.g. a device for sendingelectromagnetic waves that generates and modulates current, and conveysit to an antenna included therein for radio-frequency transmission orconveys it to a LED, laser, or other light source included therein foroptical transmission) or a wireline transmitter (e.g. that includesoutput terminal(s) coupled to transistor(s) included therein to generateelectrical signal(s) for transmission across one or more wires).

Hence a field of view 212 (FIGS. 2A and 29C) of the endoscope is a rangeof angles through which an image of the gastrointestinal tract iscaptured by at least one camera, optionally cropped and supplied to thetransmitter. Therefore, in several embodiments of the invention, anendoscope's field of view 214 is effectively (an “effective field ofview”) smaller than a typical camera's field of view traditionallydefined by lens 202's field of view 2993 (FIG. 29C) and also limited bysensor 232's size (thereby defining its own field of view 2992). Asillustrated in FIG. 29C, a region 2994 of an image formed in a plane2991 inside the camera is inherently cropped by the position anddimensions of sensor 232. Additionally, in embodiments of the typeillustrated in FIG. 29C, a processor within the endoscope furtherdiscards another region 2995 in plane 2991 even though additional datarepresenting region 2995 is captured by sensor 232. Accordingly, theendoscope's field of view 214 is defined by a region 2999 of the sensorwherein image data of a diagnosable image is generated.

In several embodiments illustrated in FIG. 30, short-range source 206(described above and shown in FIGS. 2A, 2D and 2E) is centered in aradial plane 3002 while long-range source 205 is centered in a differentradial plane 3001. Planes 3001 and 3002 are radial relative to housing201, i.e. each of these planes passes through the longitudinal axis 222which is at the center of the cross-section of housing 201. Radialplanes 3001 and 3002 make are at angles O1 and O2 respectively, relativeto a plane 3000. Plane 3000 passes through seams 1103 and 1104 at whichthe two halves 1101 and 1102 of the optical element 1100 are glued toone another. Angles O2 and O1 may be same as or different from oneanother depending on the embodiment. In an illustrative embodiment,angle O2 is 25° and angle O1 is 22.5°. However, as will be apparent tothe skilled artisan, different values of angles O2 and O1 are used inother embodiments, depending on the relative position of the compoundparabolic concentrators formed within optical element 1100. The precisevalues of angles O2 and O1 in a specific embodiment may be determined byexperiment and/or trial and error.

Some embodiments of an endoscope of the type described above use aradially-symmetric optical element within a camera, as illustrated inFIGS. 31 and 32. Specifically, a capsule endoscope of certainembodiments houses a panoramic camera which includes a single objectivelens 3100 (FIG. 31) whose optical axis 3101 is substantially parallel to(e.g. within 20° of) the longitudinal axis 222 of the capsule endoscope.FIG. 32 shows another embodiment wherein the capsule endoscope houses amirror 3200 with its optical axis 3202 being also substantially parallelto the longitudinal axis 222.

Panoramic cameras of the type shown in FIG. 31 provide a Field of View(FOV) that exceeds 180° but with an obscuration at the center of theFOV. For example, the FOV in one embodiment is a full 360° in latitude(i.e. in all radial directions in the cross-sectional view shown in FIG.30). In this example, the longitudinal range of angles for the FOV spanonly 40° relative to a lateral plane perpendicular to the longitudinalaxis and passing through the center of lens 3100, i.e. the longitudinalFOV 3102 (FIG. 31) of this example spans 200° less 160° (angle ofobscuration). Note that half of the angles 200° and 160° are illustratedin FIG. 31 as 3103 and 3104 respectively.

Panoramic annular lens 3100 of FIG. 31 is similar or identical topanoramic annular lenses (PALs) described in, for example, U.S. Pat. No.4,566,763 and U.S. Pat. No. 5,473,474 both of which are incorporated byreference herein in their entirety. A capsule endoscope with a PALimaging system is also described in US Patent Publication 200801438222entitled “In vivo sensor with panoramic camera” filed by Kang-Huai Wangand Gordon Wilson on Dec. 19, 2006 which is incorporated by referenceherein in its entirety.

In the embodiments illustrated in FIG. 32 surface 3201 of mirror 3200 isformed as a conicoid surface of revolution, such as a spheroid,paraboloid, hyperbaloid, or any aspheroidal shape depending on theembodiment. Note that in certain embodiments of FIG. 32, the objectiveoptical system 3250 is similar or identical to a corresponding objectiveoptical system of the type described in US Patent Publication20050049462 entitled “Capsule Endoscope” filed by Masafumi Kanazawa onAug. 31, 2004 which is incorporated by reference herein in its entirety.Several embodiments as shown in FIGS. 31 and 32 have a camera with acentral axis coincident with a longitudinal axis 222 of a housing of thecapsule endoscope, in other embodiments these two axes are not aligned,and may even be oriented at a predetermined angle relative to oneanother depending on the embodiment.

The image exposure in certain illustrative embodiments of the inventionis determined by averaging pixel levels sensed in pre-defined sectors ofsensor regions Q1-Q4 illustrated in FIG. 2O. The sector positions areadjusted to account for possible decenter of images on the sensors, but,roughly speaking, each of the four sensor regions Q1-Q4 illustrated inFIG. 2O is subdivided into 4 sectors. The 16 sectors of a sensor 232(FIG. 24) are labeled as shown in FIG. 20 relative to labels of thecorresponding LEDs. Sensor regions Q1-Q4 map to a cylindrical field ofview, and therefore sensor regions Q1 and Q4 are adjacent to oneanother.

Note that in some embodiments, each of sensor regions Q1-Q4 is onequadrant in a single monolithic sensor chip 232 as shown in FIG. 24. Theilluminated scene is imaged by the camera onto the single monolithicsensor chip that captures four images in four sensor regions, labeledQ1-Q4. Each sensor region is itself divided into four sectors by twoperpendicular lines and the sectors are labeled with sector numbers (asshown in FIG. 24). As noted above, each sector is labeled relative tothe corresponding LED as shown in FIG. 20.

Several embodiments of an endoscope use sixteen LEDs, including eightLEDs located above an annular mirror 218 (FIG. 2E) that are labeled withodd numbers, and eight LEDs located in a lower portion of the endoscopethat are labeled with even numbers. The sixteen LEDs are all turned onsequentially, one after another, in rapid succession, to generate apanoramic image on sensor 232.

The luminous energy recorded by each pixel in the sensor chip isproportional to the illuminating luminous energy incident upon thatportion of the scene imaged onto the pixel. The constant ofproportionality depends, or efficiency with which scattered light iscollected by the sensor, depends on many factors including thereflectance of the objects in the scene, the f# of the camera. Note thatf# is the light-collection ability of a lens, the smaller the f# themore light is collected. For example, the f# of a lens is related as aninverse square of the amount of light collected.

The location and orientation of the LEDs is such that each LEDprincipally affects the illumination of one corresponding sensor sector,although “cross talk”, i.e. illumination of a sector by anon-corresponding LED, also is significant. For the ith sector, theexposure is given by averaging the signal levels a of the N pixels inthe sector

$v_{i} = {\frac{1}{N}{\sum\limits_{k}^{N}\; {\sigma_{k}^{1/\Gamma}.}}}$

In the above equation, v denotes the radiant energy (also calledluminous energy) received by the sensor and integrated over an area.If the averaging is done before gamma correction, Γ=1. Otherwise, Γ isthe gamma factor, e.g. 2.2. Averaging after gamma correction may producebetter results with high contrast images, but that is an open question.Let u_(i) ^((n)) be the luminous energy of the ith LED for exposure n.Assuming that the LEDs have linear L-I curves, u_(i) ^((n)) isproportional to the integrated LED drive current integrated overexposure time τ

u_(i)^((n)) ∝ ∫₀^(τ)I_(i)^((n))(t) t,

Note that in the above equation, u denotes the energy output by an LED.Since illuminance adds linearly,

v=Au.

For a design of an endoscope as illustrated in FIGS. 17 and 18, A is asquare matrix with the diagonal elements dominating. A is not constantbut depends on the shape of the body cavity and the endoscope'sorientation within it. Typically, we desire the illumination to be thesame in all sectors. Let the target exposure be {tilde over (v)}_(i)=v₀.In principle the needed LED energies can be determined as

u=A ⁻¹ {tilde over (v)}.

However, A is not known exactly.The LED energies for the next frame u^((n+1)) may be estimated based onu^((n)) and v^((n)) for the current frame n

u ^((n+1)) =u ^((n)) +B({tilde over (v)}−v ^((n))).  (0.1)

If B=A⁻¹ then we expect exact convergence to the desired exposure in thenext frame. In order to make the illumination control method morestable, we estimate B such that |B_(i,j)|<|A_(i,j) ⁻¹| for all i and j.Also, we include off-diagonal elements to account for cross talk fromneighboring LEDs. The optimal matrix B depends on the endoscope and/ortissue geometry. For example, the cross talk increases as the lumen wall(i.e. wall of the body cavity, or tissue) recedes from the endoscope.Thus, the magnitude of current to off-diagonal elements increases withincreasing endoscope-lumen distance. The lumen distance is not known.However, u_(i) is correlated to the endoscope-lumen distance soB_(i,j)=ƒ(u_(i), j). This relationship will be determined throughraytrace modeling and experimentation.

Given these relationships, u^((n+1)) may be estimated straightforwardly.

$B_{i,j} = \left\{ {{\begin{matrix}{f_{1}\left( u_{i} \right)} & {j = i} & {i\mspace{14mu} {odd}} \\{f_{2}\left( u_{i} \right)} & {j = i} & {i\mspace{14mu} {even}} \\{f_{3}\left( u_{i} \right)} & {j = {i + 1}} & {i\mspace{14mu} {odd}} \\{f_{4}\left( u_{i} \right)} & {j = {i - 1}} & {i\mspace{14mu} {even}} \\{f_{5}\left( u_{i} \right)} & {j = {i \pm 2}} & {i\mspace{14mu} {odd}} \\{f_{6}\left( u_{i} \right)} & {j = {i \pm 2}} & {i\mspace{14mu} {even}} \\{f_{7}\left( u_{i} \right)} & {{j = {i - 1}},{i + 3}} & {i\mspace{14mu} {odd}} \\{f_{8}\left( u_{i} \right)} & {{j = {i + 1}},{i - 3}} & {i\mspace{14mu} {even}} \\0 & {otherwise} & \;\end{matrix}\mspace{14mu} {and}j}->\left\{ \begin{matrix}{j + 16} & {j < 1} \\{j - 16} & {j > 16}\end{matrix} \right.} \right.$

The functions ƒ_(m)(u_(i)), m=1, 2, . . . , 6, are tabulated.

${f_{m}\left( u_{i} \right)} = \left\{ \begin{matrix}{{\rho\Gamma}\; a_{1\; m}} & {0 < u_{i} < {\rho \; u_{1}}} \\{{\rho\Gamma}\; a_{2\; m}} & {{\rho \; u_{1}} < u_{i} < {\rho \; u_{2}}} \\\vdots & \; \\{{\rho\Gamma}\; a_{n\; m}} & {{\rho \; u_{n - 1}} < u_{i} < {\rho \; u_{n}}}\end{matrix} \right.$

where n is a reasonably small number ˜4. Γ is a feedback gain. If Γ istoo high, the convergence will be unstable. If Γ is too low, theconvergence will be slow. ρ is adjusted to account for differences inthe average reflectivity of the object (test cylinder or colon). For thewhite test cylinder ρ≈0.95. For the colon ρ=0.3.

The bottom LEDs (which are used for short range illumination) moststrongly affect the exposure when the lumen is close and the top LEDsare more effective when the lumen is farther away. Accordingly, toconserve energy in the endoscope, the value of u_(i) is capped at amaximum value u_(max upper) for i odd. After initially calculatingu^((n+1)), any upper LED values of the vector that exceed u_(max upper)would be reduced to that value. Depending on the embodiment, upper LEDvalues may be limited differently, e.g. by using a different matrix B.

If the lumen is touching the endoscope, the top LEDs (which are used forlong-range illumination) have very little impact on the exposure. Thus,it could happen that the amount of current to these LEDs is increased toa high value, which would waste power. When this condition occurs, theenergy of the upper LED (in the long-range light source) is limited tomaximum value u_(max upper). The best indicator of this condition is theLED level for a neighboring lower LED. If u_(i+1) ^(n)<b₁, then werequire u_(i) ^(n)<b₂.

If an LED drive u_(k) is capped and {tilde over (v)}_(k)−v_(k) ^((n))>0then u_(k) does not change in the next iteration. However, the matrixelements are based on the assumption that it will increase and otherLEDs may not converge properly. Similarly, if u_(k)=u_(min), whereu_(min) is the minimum LED drive (typically zero or one) and {tilde over(v)}_(k)−v_(k) ^((n))<0, a similar problem occurs. To remedy the problemwith either set of conditions, we temporarily set some matrix elementsto zero

$B_{i,j}^{\prime} = \left\{ \begin{matrix}0 & {{j = k},{j \neq i}} \\B_{i,j} & {otherwise}\end{matrix} \right.$

Determining LED drive levels: u_(i) is the luminous energy. Due tovariations among LED efficiencies, the electrical charge required toachieve that energy will vary somewhat. Let u_(i)=α_(i)q_(i), whereq_(i) is the LED drive value and α_(i) is the efficiency of the ith LED.It may be convenient to choose the nominal efficiencies to beapproximately one q_(i) and u_(i) fall between 0 and 255.

The efficiencies can be determined by calibration. In the currentfinal-test plan, the illumination control method is run with theendoscope in a uniform white cylinder for a number of iterations. Theresulting image is examined for uniformity. Also, the LED drive levelsq_(i) are recorded. If the test conditions are symmetric, then all theluminous energies should be equivalent for all upper and lower LEDsrespectively.

u _(i) =u _(odd)=α_(i) q _(i) for all i odd

u _(i) =u _(even)=α_(i) q _(i) for all i even

Thus, the efficiencies α_(i) are deduced.

During calibration, α is not known. A constant is chosen as an initialguess. A typical value might be 0.2 mA-1, if the maximum value of u is255. The initial guess value may be 1.

The above-described principles are implemented by appropriatelyprogramming a processor in an endoscope to perform a method illustratedin FIG. 21. Specifically, the processor starts in act 2101 (see FIG.21), by setting the frame number to zero. Then in act 2102, theprocessor looks up initial values of LED drives namely the vector u(n)and LED drive cap values u(cap). The initial values in vector u(n) atthe beginning when the endoscope is first turned on are all 0, in oneexample. Note that u(cap) is determined by experiment and is set to aslow as possible to minimize ghosts while still achieving good uniformityat a variety of distances D1-D4 as described above in reference to FIGS.2I and 2K. Note that the energy of the lower LED (in the short-rangelight source) is limited to the maximum value u(cap).

Referring to FIG. 21, the processor enters a loop starting with act2103. Note that act 2103 itself is repeatedly performed for each elementu_(i) ^((n)), wherein the processor checks if u_(i) ^((n)) is greaterthan ui(cap) and if so saves the value of ui(cap) as u_(i) ^((n)). Afterperforming act 2103 for each element u_(i) ^((n)), the processor thenproceeds to act 2104. In act 2104, the processor sets the LED drives togenerate the current in vector u(n) and then proceeds to act 2106 tocapture the image. In act 2104, the processor also performs an act 2105to determine the matrix B(n)(u(n)) based on the LED drives,simultaneously or contemporaneously with acts 2106-2109.

Note that the values of the LED drives are proportional to u_(i) ^((n))depending on the efficiency of the LED. After act 2106, the processorgoes to act 2107 and calculates an average (or other such function) ofluminance value, for each sector of image sensor−vector v(n).

In some embodiments, the pixel values (e.g. 50,000 pixels in a sector)are simply summed up and divided by their number so as to obtain asimple average, although other embodiments may use a weighted average.Some embodiments exclude outliers (e.g. all saturated pixels or somemaximum percentage of saturated pixels). Yet another embodiment uses amedian instead of an average.

Note that in act 2107, a more complicated function than a simple averageis computed in several embodiments. For example, in some embodiments,pixels with luminance values above or below a preset threshold arerejected, i.e. not used in computing the result. In one illustrativeembodiment, the pixel value of 255 in an 8 bit number is rejected asbeing above a preset upper threshold, because this number may representany over-exposed value, even a value resulting from specular reflection.In the just-described illustrative embodiment, the pixel values of 2, 1and 0 are also rejected as being below a preset lower threshold, becausethese values may represent noise.

After act 2107, the processor goes to act 2108, and calculates adifference between target luminance vt and measured luminance for eachsector−vector (v(t)−v(n)). Typically, target luminance vt is a scalarconstant, e.g. 60 out of a maximum of 255.

Next, the processor goes to act 2109, and computes new LED drives, asu(n)=u(n)+B(n)(v(t)−v(n)). Note that in act 2109, the processor receivesthe result of act 2105, i.e. the matrix B(n)(u(n)).

After act 2109, the processor goes to act 2110 to increment n, and theniterates back to the beginning of the loop, specifically to act 2103. Agraph of timing relationships between signals between a controller, LEDsand sensors in an endoscope is illustrated in FIG. 22. Note that theLEDs are turned on during an integration time for pixels in the sensors,thereby to capture an image formed by light that is emitted by the LEDsand reflected by tissue.

As noted above, energy emitted in short-range electromagnetic radiationis capped or limited to use energy efficiently in some embodiments.Referring to FIG. 33, endoscope 200 moves from a current location 3301to a new location 3302 at which an increase Δd1 (e.g. 3 mm) in adistance d1 (e.g. 13 mm) of the short-range illumination region from thegastrointestinal tract is greater than an increase Δd2 (e.g. 6 mm) indistance d2 (e.g. 14 mm) of the long-range illumination region from thegastrointestinal tract (when measured in a common direction). Inresponse to such movement, some embodiments of an endoscope inaccordance with the invention automatically increase radiant energy E2(e.g. 5 micro Joules) emitted in the long-range electromagneticradiation from the long-range illumination region by an amount ΔE2 (e.g.1 micro Joule) which is larger than an increase ΔE1 (e.g. 0.1 microJoule) in radiant energy E1 (e.g. 5 micro Joules) emitted in theshort-range electromagnetic radiation. After these increases, endoscope200 stores in its memory another portion of another image of the tractfrom the new location. The current inventor submits that it isnon-obvious to make ΔE1<ΔE2 in response to a movement which makesΔd1>Δd2. As noted above, in some embodiments E1 is capped to a maximumvalue u_(max upper). Hence, in some situations wherein such a presetlimit is reached, ΔE1 is kept at zero in order to conserve energy evenif Δd1>Δd2.

Numerous modifications and adaptations of the embodiments describedherein will be apparent to the skilled artisan in view of thedisclosure.

For example, some embodiments of a device include a housing sufficientlysmall to be insertable into a gastrointestinal tract of a human, acamera enclosed within said housing, wherein an optical axis of thecamera intersects the housing at an intersection point, a first sourceof electromagnetic radiation enclosed within said housing, with firstelectromagnetic radiation from the first source exiting through a firstregion of the housing on operation of the first source, wherein thefirst source is positioned within the housing such that the first regioncontains the intersection point of the optical axis with the housing, asecond source of electromagnetic radiation enclosed within said housing,with second electromagnetic radiation from the second source exitingthrough a second region of the housing on operation of the secondsource, wherein the second source is positioned within the housing suchthat the intersection point of the optical axis with the housing islocated outside the second region.

As another example, certain embodiments of a device include a housingsufficiently small to be swallowed, a camera enclosed by the housing,the endoscope having a field of view defined by a largest imageeffectively transmitted by the endoscope to an external computer, aplurality of sources of light enclosed within the housing, wherein eachsource in the plurality of sources has an aperture positioned within thehousing to emit rays reflected by the housing and forming a mirror imageof said aperture outside of the field of view of the endoscope.

Also, instead of using a CPC as optical element 216, alternativeembodiments of endoscope 200 in accordance with the invention useannular angular concentrators having other types of cross-sections thatmay less effectively reduce angular divergence, such as a cone or aparaboloid. In two illustrative embodiments, a concentratorcross-section that is used in an annular angular concentrator has thesame shape as a handheld flashlight's concentrator or an automobileheadlight's concentrator.

Some embodiments of an endoscope of the type described herein minimizethe amount of light received by a sensor after reflection from thehousing of the endoscope by one or more techniques, such as (a)employing optical elements (such as the CPC) to reduce a range of anglesthrough which light is emitted by a source (such as a short-rangesource) and (b) providing one or more sources (such as a long-rangesource) that emit a majority (or most) of the light through a region ofthe housing through which image forming rays (to the sensor) do notpass.

In some illustrative embodiments, a device in accordance with theinvention comprises: a housing sufficiently small to travel through agastrointestinal tract of a human, a first source of electromagneticradiation enclosed within the housing, with first electromagneticradiation from the first source exiting through a first region of saidhousing, a second source of electromagnetic radiation enclosed withinsaid housing, with second electromagnetic radiation from the secondsource exiting through a second region of said housing, a cameraenclosed within the housing; wherein the endoscope has a field of viewdefined by a range of angles through which a cropped image of thegastrointestinal tract is captured by a sensor in the camera, onoperation of the camera, wherein the cropped image is formed byreflection of at least a portion of said first electromagnetic radiationand a portion of said second electromagnetic radiation from thegastrointestinal tract, wherein the field of view intersects the housingat a third region overlapping at least a portion of the first region;and wherein the camera has an optical axis intersecting the housing at apoint in said portion of the first region overlapped by the thirdregion, the point being outside the second region.

In several illustrative embodiments, a device in accordance with theinvention includes a housing sufficiently small to be enclosed within anorgan of a human; at least one upper source of electromagnetic radiationenclosed within the housing; wherein, on operation of the at least oneupper source, electromagnetic radiation, of a first intensity that is atleast a first predetermined percentage (e.g. almost all or over 90%) ofmaximum intensity from the at least one upper source, exits through anupper illumination region of a surface of the housing; at least onelower source of electromagnetic radiation enclosed within the housing;wherein, on operation of the at least one lower source, electromagneticradiation, of a second intensity that is at least a second predeterminedpercentage (e.g. 37%) of maximum intensity from the at least one lowersource, exits through a lower illumination region of the surface of thehousing; wherein the lower illumination region is larger than (e.g. 1.2times larger or 1.5 times larger or even 5 times larger) the upperillumination region; at least one camera enclosed within the housing;wherein the at least one camera forms an image of light emitted from atleast one of the lower illumination region and the upper illuminationregion and entering the housing after reflection from a surface of theorgan through the lower illumination region.

Additionally, note that a “majority of electromagnetic radiation” asused herein refers to a majority of power.

Furthermore, note that as region 212 (FIGS. 2J, 28A-28D) demarcatesreflected light entering endoscope 200 which is used in forming adiagnosable image, any region outside of the boundary of region 212 isreferred to herein as a non-imaging region. Hence, region 211 is anon-imaging region in FIG. 28A. Accordingly, a majority ofelectromagnetic radiation emitted by a long-range light source of someembodiments exits the housing of endoscope 200 through a non-imagingregion (i.e. any region outside of boundary 212). Moreover, in suchembodiments, a majority of electromagnetic radiation emitted by ashort-range light source exits the housing of endoscope 200 outside ofthe non-imaging region, i.e. exits through the region 212.

Note that an organ as used herein can be a uterus or any part of agastrointestinal tract (such as a colon, small bowel (small intestine),esophagus, stomach, rectum). Accordingly, an apparatus as describedherein can be used to obtain images of any organ of a human or othersuch mammal.

In certain embodiments, short-range illumination region 210 issignificantly larger (e.g. several times larger, such as 2 times larger,3 times larger, or even 5 times larger) than long-range illuminationregion 211. This relationship between the two types of illuminationregions is illustrated in FIGS. 2B and 2C wherein each of overlappingregions 210A, 210B and 210C for short-range illumination areindividually larger than long-range illumination region 211, and hencetheir combination into region 210 is significantly larger than region211.

Finally, although endoscope 1900 has been illustrated in FIG. 19 asenclosing a single camera located in one dome at one end of a capsule, asimilar endoscope 3400 illustrated in FIG. 34 encloses two cameras atthe two ends of such a capsule. Specifically, endoscope 3400 has twoapertures 3405 and 3406 and two pupils P1 and P2 respectively throughwhich reflected light from a gastrointestinal tract is received by twosensors 3401 and 3402 respectively. Sensors 3401 and 3402 togetherconstitute a set of sensors that generate image data at differentpositions of endoscope 3400 relative to the tract. Image data obtainedby the set of sensors (i.e. sensors 3401 and 3402 in FIG. 34) issupplied to a transmitter 3403 that in turn supplies the image data toan external computer (after optional cropping), for use in generationand display of a diagnosable image.

What is claimed is:
 1. A device comprising: a plurality of sourcesenclosed within a housing, said plurality of sources being located in aring around a camera, each source in the plurality of sources comprisinga pair of terminals and at least one emitter of electromagneticradiation coupled to said pair of terminals; an optical element enclosedwithin said housing, the optical element being located in a path of aportion of electromagnetic radiation emitted by at least one source inthe plurality of sources so as to direct at least a fraction of saidportion of electromagnetic radiation out through the housing; whereinthe camera is positioned within the housing such that at least a portionof an image is formed in said camera by at least a fraction of saidportion of electromagnetic radiation entering the housing through atubular wall after reflection outside the housing.
 2. The device ofclaim 1 wherein: the optical element is shaped to reduce angulardivergence of said portion of electromagnetic radiation.
 3. The deviceof claim 1 wherein: the optical element comprises a mirrored surfacedefined at least by a portion of a parabola.
 4. The device of claim 1wherein said portion of electromagnetic radiation is hereinafter a firstportion, and wherein: a second portion of electromagnetic radiationexits the housing without being directed by the optical element.
 5. Thedevice of claim 1 wherein: said optical element comprises a mirroredsurface defined by an angular concentrator having an axis that passesthrough a location of said at least one source.
 6. The device of claim 1wherein the housing has a near and a far end, and wherein: the opticalelement comprises a mirrored surface offset in a longitudinal directionfrom an optical axis of the camera towards the near end; and each sourcein the plurality of sources is offset in a longitudinal direction fromthe optical axis of the camera towards the far end; and the mirroredsurface is located in a path of a second portion of electromagneticradiation emitted by at least one source in the plurality of sources soas to reflect at least a fraction of said second portion ofelectromagnetic radiation out through the housing.
 7. The device ofclaim 6 wherein the mirrored surface is annular.
 8. The device of claim6 wherein said plurality of sources are hereinafter a first plurality ofsources, the mirrored surface is on a mirror and wherein: the devicefurther comprises a second plurality of sources; and the secondplurality of sources are offset in said longitudinal direction from saidoptical axis toward the near end.
 9. The device of claim 8 wherein: thesecond plurality of sources are positioned behind the mirror which actsas a baffle to block rays originating in at least one source in thesecond plurality of sources from forming a virtual image that can becaptured by the camera.
 10. The device of claim 8 further comprising abaffle enclosed within the housing, wherein: the second plurality ofsources are positioned behind the baffle to block rays originating in atleast one source in the second plurality of sources from forming avirtual image that can be captured by the camera.
 11. The device ofclaim 1 wherein: The optical element has an input aperture facing saidat least one source and an output aperture at which said portion ofelectromagnetic radiation has reduced angular divergence; and theoptical element has an additional input aperture and an additionaloutput aperture such that an additional portion of electromagneticradiation emitted by said at least one source enters the optical elementthrough said additional input aperture and exits the optical element atsaid additional output aperture.
 12. The device of claim 1 wherein: theoptical element comprises a mirrored surface on one side of a layer; andsaid layer has another side that reflects at least a fraction of anadditional portion of electromagnetic radiation emitted by said at leastone source.
 13. The device of claim 1 wherein: a longitudinal planepasses through a point (hereinafter “intersection point”) formed byintersection of a surface of said housing with an optical axis of saidcamera, the longitudinal plane further passes through a center ofcurvature C of an arc AB, the arc AB being defined by intersection ofsaid surface of said housing with a lateral plane parallel to theoptical axis and passing through said intersection point, the lateralplane and the longitudinal plane being oriented perpendicular to oneanother; and the optical element limits angular divergence of at leastsome illumination rays emitted from said at least one source such that aprojection on to said longitudinal plane, of an illumination ray in saidmajority, after reflection from said intersection point, makes an angleθi with a normal to said surface of said housing such that θi>θ_(FOV)+αwherein θ_(FOV) is half angle of a field of view of the camera projectedin the longitudinal plane and α is an angle between said normal and saidoptical axis.
 14. The device of claim 1 wherein: a first illuminationray emitted by said at least one source is incident on the housing withangle of incidence θ_(i) and is reflected with an identical angle ofreflection relative to a line N that bisects an angle formed by saidfirst illumination ray and a reflected ray resulting from reflection ofsaid first illumination ray by said housing; a point U exists at theintersection of a first line collinear with the incident ray and asecond line collinear with the reflected ray; a first image forming rayforms an angle σ with line N, said first image forming ray beingcomprised in a plurality of image forming rays, said plurality of imageforming rays forming a cropped portion of said image supplied to atransmitter comprised in said device; additional illumination rays fromsaid at least one source are restricted in angle such that θ_(i)>σ for amajority of pairs of any additional illumination ray incident on thehousing and a corresponding additional image forming ray comprised insaid plurality of image forming rays; the first image forming ray, whenlocated within a free space between the housing and the camera, iscollinear to a line passing through said point U and a pupil of thecamera; and said line is coplanar with said first illumination ray andsaid reflected ray.
 15. The device of claim 1 wherein: the opticalelement has an annular shape.
 16. The device of claim 15 wherein: theoptical element comprises a plurality of spokes between an innersidewall and an outer sidewall; and the a mirrored surface is betweenwalls of two adjacent spokes, on one of the inner sidewall or the outersidewall.
 17. The device of claim 16 wherein the mirrored surface ishereinafter a first mirrored surface, and wherein: a second mirroredsurface is between said walls of two adjacent spokes, on the other ofthe inner sidewall or the outer sidewall.
 18. The device of claim 17wherein: edges of the first mirrored surface, the second mirroredsurface and said walls of the two adjacent spokes define a boundary ofan input aperture of the optical element; and said at least one sourceis located directly facing the input aperture.
 19. The device of claim15 wherein: said at least one emitter comprises a light emitting diode(LED) encapsulated within a cavity of a package; and the optical elementis mounted on the package with at least a portion of the outer sidewallof the optical element overhanging an opening of the cavity.
 20. Thedevice of claim 19 wherein: said opening of the cavity is of an arealarger than an area of an input aperture of said optical element facingsaid at least one source.
 21. The device of claim 1 wherein: the opticalelement is on a first side of a plane and said at least one source is ona second side of said plane and all electromagnetic radiation from saidat least one source is emitted on the second side of said plane.
 22. Thedevice of claim 1 further comprising an additional wall enclosed withinthe housing, wherein: a plurality of paths correspond to a plurality ofrays originating from a specific source in the plurality of sources, theplurality of paths pass through the additional wall to reach the housingand the rays reflect therefrom to form within said housing, a mirrorimage of the specific source, in the absence of the additional wall; andthe additional wall is opaque and positioned adjacent to the specificsource to block passage of the plurality of rays along said paths toprevent said formation of said mirror image by said plurality of rays.23. The device of claim 22 wherein: the additional wall is annular. 24.The device of claim 1 further comprising a baffle enclosed within thehousing, wherein: the baffle is positioned to block rays originating inat least one source in the plurality of sources from forming a virtualimage that can be captured by the camera.
 25. The device of claim 1wherein: the optical element comprises a lens.
 26. The device of claim25 wherein: the lens is a collimating lens.
 27. A method of in vivoimaging comprising: emitting electromagnetic radiation by at least onesource in a plurality of sources enclosed within a housing; wherein theplurality of sources are located in a ring, each source in the pluralityof sources comprising a pair of terminals and at least one emitter ofelectromagnetic radiation coupled to said pair of terminals; wherein anoptical element is located in a path of a portion of electromagneticradiation emitted by said at least one source; wherein at least afraction of the portion of the electromagnetic radiation is directed bythe optical element to exit the housing; and sensing an image in atleast one camera enclosed within the housing; wherein at least a portionof the image is created in said at least one camera by at least afraction of said portion of said electromagnetic radiation entering thehousing through a tubular wall after reflection outside the housing. 28.The method of claim 27 wherein: the optical element comprises a mirroredsurface defined at least by a portion of a parabola
 29. The method ofclaim 27 wherein: the optical element is annular.
 30. The method ofclaim 27 wherein: at least a portion of said optical element is definedby an angular concentrator having an axis that passes through a locationof said at least one source.
 31. The method of claim 27 wherein thehousing has a near and a far end, and wherein: the optical elementcomprises a mirrored surface offset in a longitudinal direction from anoptical axis of the camera towards the near end; and each source in theplurality of sources is offset in a longitudinal direction from theoptical axis of the camera towards the far end; and the mirrored surfaceis located in a path of a second portion of electromagnetic radiationemitted by at least one source in the plurality of sources so as toreflect at least a fraction of said second portion of electromagneticradiation out through the housing.
 32. The method of claim 27 wherein:the optical element is on a first side of a plane and said at least onesource is on a second side of said plane and all electromagneticradiation from said at least one source is emitted on the second side ofsaid plane.
 33. The method of claim 27 wherein: said endoscopecalculating an average luminance value for each sector in a plurality ofsectors used to sense said image; said endoscope calculating adifference between the average luminance value calculated for eachsector and a target luminance value for said each sector; and saidendoscope computing a drive current for generating the electromagneticradiation, based at least partially on said difference.
 34. The methodof claim 33 wherein: a change in said drive current is obtained based ona linear combination of a plurality of said differences individuallycalculated for each sector in said plurality of sectors.
 35. The methodof claim 31 wherein: the second mirrored surface is on a mirror whichacts as baffle to block rays originating in at least one source in thesecond plurality of sources from forming a virtual image in said camera.36. The method of claim 27 wherein: the optical element comprises alens.